Genchem1

Question 0

what is an atom made up of?

Answer 0

Protons Neutrons and Electrons. The number of protons is the atomic number which it has on the periodic table.

Question 1

how many atoms would fit across the width or your hair?

Answer 1

about a million thats how small they are.

Question 2

how does electron neutron and protons masses compare?

Answer 2

neutron and proton are the same electron is about 1800 times less

Question 3

what is the number of protons + the number of neutrons?

Answer 3

The mass number

Question 4

if youre talking about a specific atom for example carbon. Can the number of protons change and still be considered carbon?

Answer 4

No they cant, the number of protons never changes. However the number of neutrons can change and the atom is still considered carbon just a different form. these are called isotopes

Question 5

how are electrons arranged around the nucleus?

Answer 5

There are energy levels in which these electrons fall in. They will always try to fill the closest orbital first. Which is closest to the nucleus

Question 6

how do you know how many electrons are in a atom?

Answer 6

The number of electrons is equal to the number of protons which is the atomic number on the periodic table

Question 7

how many electrons can the first three levels hold?

Answer 7

2 , 8, 8

Question 8

what does the group number the atom is found in on the periodic table tell you about that atoms electrons?

Answer 8

The group number will tell you how many atoms are located in the outer energy level.

Question 9

what happens to the energy level of electrons as they are further away from the nucleus in there orbitals

Answer 9

The energy goes up.

Question 10

Just a note

Answer 10

circles around the nucleus to represent energy levels mislead us. Electrons dont actually orbit the nucleus

Question 11

what hold nuclei ( protons and neutrons ) together?

Answer 11

Strong nuclear forces bind nuclei together. Electro static pulls them away

Question 12

how could you represent an atom to show how many protons it has and how many protons and neutrons it has?

Answer 12

12C
6

the C should be much bigger a lot of the times the mcat will represent the A as the mass number (protons + Neutrons) and Z as the atomic number (number of protons)

Question 13

what is the bohr model?

Answer 13

the bohr model is the representation of how the atom is set up. The nucleus is in the middle with pros and neutrs. There are then electron levels in which the electrons reside in. They dont orbit the nucleus however.

Question 14

what is an isotope? Do they all have odd mass numbers?

Answer 14

an isotope is basically just a different version of that atom. The atomic number (# of protons) will still be the same but the change in the number of neutrons is what gives an isotope. No they dont, for example carbon 14 has 7 protons and 7 neutrons. Making the mass number 14 which is even .

Question 15

what is a cation? what is an anion?

Answer 15

A cation is a positively charged atom ( less number of electrons than protons). An anion is neg charged ( more elec than pros)

Question 16

do metals form cations or anions?

Answer 16

metals from cations. non metals for anions.

Question 17

A student introduces a particle of unknown identity between two oppositely charged electrodes and notes that it accelerates toward one of the two electrodes? what could this particle not be?

Answer 17

A neutron. Cation and anion both have charge and so do pro and elc

Question 18

what happens to atomic radius as you go down a column on the p table?

Answer 18

The radius gets bigger. This is obvious because the atomic number increases as well as do the electrons making the radius bigger.

Question 19

What happens to radius as you go across the periodic table?

Answer 19

The atoms get smaller which in turn decreases the radius of the atom. However, you have to ignore the noble gases they DONT follow this rule.

Question 20

what is ionization energy?

Answer 20

The energy required to remove an electron from the neutral state of an atom or turn an atom into a cation

Question 21

What is the trend of ionization energy on the periodic table?

Answer 21

The ionization energy goes from left to right. As the you to the right the energy required to remove an electron is far more than the atoms on the left side of the table. This is because an atom is in its most stable form when the outer most shell of that atom is full. So the atoms in the first column, if they lose one they have there outer most shell full. Also as you go down the table the number of electrons increases for each atom. This means that they are further away from the nucleus so they are even more willing to give up there electron because the nucleus isn’t attracting them as much as the electrons that are closer to the nucleus

Question 22

what is electronegativity?

Answer 22

it basically the hogging of electrons. If you have a water molecule there will be more electrons around the oxygen than hydrogens.

Question 23

What would be the periodic trend for electronegativity?

Answer 23

Well think about ionization energy. The atoms that want to hold on to their electrons more because they are stable with how they are are going to be more electronegative.

Question 24

what is metallic nature or character?

Answer 24

This is very similar to the ionization energy of an atom. When something has a metallic character it gives up its electrons easier. So the atoms in the bottom left that have a single electron in its outer most shell which is far ways from the nucleus because it has so many protons, will have a higher metallic character than say Fluorine that doesn’t give up its electrons easy

Question 25

what is the atomic radius?

Answer 25

The atomic radius is basically just how big the atom is. The atom doesnt have a perfectly spherical shape so this is hard to measure. Sometime people measure it by taking some two atoms bonding them and then diving that length of the bond by two.

Question 26

whats the periodic trend for atomic radii

Answer 26

As you go from left it right the atoms get more protons and thus more electrons. The electrons however stay in the orbital and don’t get further away so this cause the nucleus to pull and the electrons and decrease the size. Top to bottom however gains electrons too but these electrons aren’t in the same orbital so they get further away from the nucleus making them bigger.

Question 27

how atomic radi trends work

Answer 27

From lithium to fluorine, those electrons are all in the 2-level, being screened by the 1s2 electrons. The increasing number of protons in the nucleus as you go across the period pulls the electrons in more tightly. The amount of screening is constant for all of these elements.

Question 28

what is electron affinity?

Answer 28

Its basically the energy release when an atom gains an electron.

Question 29

Whats a good way to determine if something has a high electron affinity?

Answer 29

If the atom has a stronger attraction toward electrons. When they come in contact more energy will be released.

Question 30

where is electrons affinity mainly happen? what groups on the periodic table?

Answer 30

Mainly 6 and 7. As you go down electron affinity decreases but Florine is an exception. You would think Florine is higher than Chlorine but Florine is less.

Question 31

Metals

Answer 31

Usually have 1-3 electrons in their outer shell.
Lose their valence electrons easily.
Form oxides that are basic.
Are good reducing agents.
Have lower electronegativities.

Question 32

Non metals

Answer 32

Usually have 4-8 electrons in their outer shell.
Gain or share valence electrons easily.
Form oxides that are acidic.
Are good oxidizing agents.
Have higher electronegativities.

Question 33

Where are the alkali metals on the p table?

Answer 33

Alkali i think of basic, so like sodium potassium. This group is on the far left. don’t count hydrogen though.

Question 34

Alkaline (earth) metals p table?

Answer 34

the group right next to the alkali metals. This will have like magnesium ect.

Question 35

where are the transition metals?

Answer 35

the middle of the periodic table

Question 36

The lanthanides p table?

Answer 36

these is the first row down under. Should be inserted in as one but took it out so they could group it. look at atomic number.

Question 37

actinides?

Answer 37

right below the lanthanides. look at atomic number and it will show where it should be located .

Question 38

noble gases?

Answer 38

far right. Helium ect

Question 39

halogens?

Answer 39

Florine and down

Question 40

s d p f blocks?

Answer 40

s is the far left, it includes helium as well. d block is all the middle elements. p is the elements on the right. f is the lower two rows (lanthanides and actinides)

Question 41

what is a good way to think of metals?

Answer 41

metals are large atoms with loosely held electrons. These electrons are held loosely because metals like to form positive ions.

Question 42

what are some good characteristics of metals?

Answer 42

lustrous, ductile, malleable, and good conductors of heat and electricity .

Question 43

how can you think of non metals?

Answer 43

non metals are just smaller atoms that like to hold on to their electrons.

Question 44

do non metals form anions or cations?

Answer 44

anions, they hold on to there electrons which makes them more so to gain an electron

Question 45

do metals have a higher melting point than non metals?

Answer 45

no

Question 46

what kind of bond do non metals form with non metals?

Answer 46

covalent

Question 47

why does size matter?

Answer 47

all the trends can base off of the atomic radius of an atom. Smaller atoms nuclei is closer to there valence electrons so those electrons are held more tightly to the positively charged nucleus. which causes an atom to be more electronegative, have higher ionization energy, greater electron affinity, and less metallic character than a larger atom.

Question 48

Are larger atoms better at stabilizing charges? Why or why not?

Answer 48

?

and larger atoms have d orbitals where they can “house” extra electrons

Question 49

Families in the same column will behave similar in what ways?

Answer 49

both physically and chemically SiH4 and CH4 will behave similar.

Question 50

why when atoms increase in size do the electrons in the valence shield feel less of a effective nuclear charge?

Answer 50

because the electrons in lower orbitals are blocking this nuclear charge. (basically pulling in on is what effective nuclear charge means)

Question 51

Electron affinity- down and up and across what happens?

Answer 51

As you go down it decreases and as you go to the left it decreases.

Question 52

Electronegativity trends?

Answer 52

As you go down it decreases as you go to the right it increases.

Question 53

Ionization energy trends?

Answer 53

?

Question 54

atomic radius trend?

Answer 54

as you go down it gets bigger, as you go to the right it gets smaller.

Question 55

metallic character trend?

Answer 55

as you go down it increases. As you go to the right it decreases.

Question 56

do electrons orbit?

Answer 56

no they inhabit a space know as an orbital

Question 57

whats a good way to think about orbitals?

Answer 57

a region of space in which an electron or electrons live. We know that depending on the orbital in which its in it will have different amounts of energy

Question 58

what does the 1 and s mean orbital 1s?

Answer 58

1 refers to the energy level that is closest to the nucleus and the s tells you about the shape of the orbital .

Question 59

what does a p orbital look like?

Answer 59

it looks like two balloons tied at the nucleus

Question 60

at any one energy level is it possible to have three p orbitals?

Answer 60

yes, but not at energy level 1 this one has s character.

Question 61

d orbitals.

Answer 61

In addition to s and p orbitals, there are two other sets of orbitals which become available for electrons to inhabit at higher energy levels. At the third level, there is a set of five d orbitals (with complicated shapes and names) as well as the 3s and 3p orbitals (3px, 3py, 3pz). At the third level there are a total of nine orbitals altogether.
At the fourth level, as well the 4s and 4p and 4d orbitals there are an additional seven f orbitals - 16 orbitals in all. s, p, d and f orbitals are then available at all higher energy levels as well.

Question 62

orbitals

Answer 62

You can think of an atom as a very bizarre house (like an inverted pyramid!) - with the nucleus living on the ground floor, and then various rooms (orbitals) on the higher floors occupied by the electrons. On the first floor there is only 1 room (the 1s orbital); on the second floor there are 4 rooms (the 2s, 2px, 2py and 2pz orbitals); on the third floor there are 9 rooms (one 3s orbital, three 3p orbitals and five 3d orbitals); and so on. But the rooms aren’t very big . . . Each orbital can only hold 2 electrons.

Question 63

Electron Configuration

Answer 63

For example, although we haven’t yet met the electronic structure of chlorine, you could write it as 1s22s22p63s23px23py23pz1.

Notice that the 2p electrons are all lumped together whereas the 3p ones are shown in full. The logic is that the 3p electrons will be involved in bonding because they are on the outside of the atom, whereas the 2p electrons are buried deep in the atom and aren’t really of any interest.

Question 64

what are the two short cuts you can use when writing out electron configuration?

Answer 64

you dont have to write out 2p 2px 2py 2px unless 2 is the outer most energy level. Also you can start from Ne to shorten up the line
S 1s22s22p63s23px23py13pz1 [Ne]3s23px23py13pz1

Question 65

electron configuration

Answer 65

There is strong evidence for this in the similarities in the chemistry of elements like sodium (1s22s22p63s1) and potassium (1s22s22p63s23p64s1)

Question 66

what does the period of the row tell us about electron configuration?

Answer 66

This tells us what energy level it goes to 1,2,3 ect

Question 67

what electrons are in a higher energy state Ti 1s2 2s2 2p6 3s2 3p6 3d2 4s2?

Answer 67

d orbital electrons are going to contain a higher energy than the 4p orbital ones. But the 4s2 are the valence so they are going to react if they do.

Question 68

what is an energy level?

Answer 68

The energy level represents the energy level of the electrons in atoms. The bohr model explains this. These are quantized meaning that they look like stair steps. Electrons can be in energy level 1 or two but never in between.

Question 69

how does an electron gain or loose its energy?

Answer 69

usually through a photon of light. Because electrons are quantized they can just move from energy level to energy level. They have to be struck will an amount of equal to the difference. So in other words if an electron is at the lowest state with 0 energy and it wants to move up to an energy level that requires 4ev then thats how much energy of light photon it must absorb.

Question 70

will electrons absorb an amount of energy that isnt equal to the difference in energy between the two levels?

Answer 70

No, it will pass through it. The energy that strikes the photon must be equal to difference in energy between the two levels. so say 0 and the next level you need 4ev. If an electron is struck by a photon with an energy that is lower other than the difference in energy between two energy levels in that atom, the photon will pass through the atom without being absorbed. If an electron drops to a lower energy level, energy is released and the amount released is the exact same amount in the difference between the two energy levels.

Question 71

what is the photoelectric effect?

Answer 71

when light is shown on a metal surface this can cause electrons to escape because it gives them energy

the kinetic energy of the electrons is linearly proportional to the frequency of the incident radiation above a threshold value of ν0 (no current is observed below ν0), and the kinetic energy is independent of the intensity of the radiation.

-the number of eimitted electrons (i.e. the electric current) is proportional to the intensity and independent of the frequency of the incident radiation above the threshold value of ν0 (no current is observed below ν0).

Question 72

what is the energy called that is expended when an electron escapes the metal in the photo electric effect?

Answer 72

This is called the work function of the metal. the energy of the electron is then the energy of the photon-work function= energy of electron

Question 73

What is the work function?

Answer 73

If you bomb certain metals with energy, this can cause the electrons to be ejected from there outer most shell ( the valence electrons). The amount of energy required to do so is called the work function. This only relates to metals so dont get it confused will ionization energy.

Question 74

what happens if you add less energy than the work function? more energy than the work function?

Answer 74

the electrons wont be ejected, the excess energy will be transferred into kinetic energy.

Question 75

what is the equation to see how much KE an electron may have when it get ejected from a metal?

Answer 75

KE = E-Φ E is the amount of energy added and KE is the KE of the ejected electron. E can also be replaced by hf to give E=hf
h=planks constant (which is alway given) and f= frequency

Question 76

how could you calculate the energy of a photon only by knowing the velocity and wavelength?

Answer 76

if you know the velocity and wave length you can find the frequency because v = wavelength * frequency then you know planks which would give you the energy

Question 77

A certain metal is know to have a work function of 500J. If a photon strikes the surface of the metal, what will be the result?

Answer 77

they wont be ejected because there will be 0 velocity? the work function is the amount of energy it needs to exceed in order for the electron to be ejected.

Question 78

what is frequency?

Answer 78

Frequency describes the number of waves that pass a fixed place in a given amount of time.

Question 79

What if you have two energy sources of light striking a metal will 350 J and 450 J the work function of the metal is 250 J. Which one will eject more electrons?

Answer 79

They will eject the same amount. Energy doesnt have to do with the amount ejected the frequency of the wave does.

Question 80

what is radio active decay?

Answer 80

its when unstable atoms change their chemical composition over time. And all the action is happening in the nucleus with the protons and neutrons and there positrons and neutrons.

Question 81

what is alpha decay?

Answer 81

Alpha decay the loss of one He nucleus. That is the atom loses two protons and two neutrons. He has a atomic number of 2 and mass number of 4.

Question 82

what is beta decay?

Answer 82

The neutron feels like changing into a proton, so the neutron itself loses an electron which then causes it to have a positive charge and therefore a proton.

Question 83

What is electron capture?

Answer 83

a type of radioactive decay in which a proton is changed into a neutron by the capture of an electron.

Question 84

Positron emission?

Answer 84

A proton is changed into a neutron by the expulsion of a positron.

Question 85

what is gamma emission?

Answer 85

Gamma rays are usually emitted as a byproduct of the types of decay outlined above. Gamma decay does not change the number of nucleons.

Question 86

how should you think about what a neutron is?

Answer 86

a neutron is basically just a proton + electron

Question 87

how should you think about what a proton is?

Answer 87

proton = neutron + a positron

Question 88

Often the MCAT will use conservation of momentum and radioactive decay in one.

If an element of 56Fe originally at rest ejects an alpha particle with a speed of 2.0 * 10^5 m/s, what is the identity of the new element formed and what is its velocity?

Answer 88

well it would lose 2 neutrons and 2 protons so there would be 24 protons and 28 neutrons so the element would be Cr. Then use conservation of momentum to solve.

Question 89

what is the half life (t1/2) or something?

Answer 89

this is the amount of time required for exactly one half of the mass of that substance to disappear due to radioactive decay.

Question 90

what are the three variables they typically give you in a half life problem?

Answer 90

the half life (t1/2) , time elapsed (t), and the amount of the substance (g)

Solve these half life conceptually in your head 50 grams it has a 10 year half life. what will it be after 20 years? 12.5 grams

Question 91

you have 500 g and the half life is 10 years how much will there be after 40 years?

Answer 91

31.25 grams

Question 92

For half life they may give you the intial and final concentrations of a substance plus the amount of time elapsed and ask you to solve for the half life. how would yo do this?

Answer 92

first decide how many times the substance had to be cut in half to go from the initial to the final value (ie the number of half lives it took). Dived the total time elapsed by the number of half lives it took to get the length of each half life.

Always take notes when doing half lives so you dont make any mistakes.

Question 93

what is the difference between anit bonding orbitals and bonding orbitals? what do each look like?

Answer 93

• Anit boding orbitals are higher in energy than bonding orbitals
• Bonding orbitals contain electrons that are “in phase” and are said to be attractive. Anti bonding orbitals contain electrons that are out of phase and are said to be repulsive.

for a bonding the two orbitals form the atoms come together and form as one. anti bonding they spit into a higher energy orbital and a lower energy orbital .

Question 94

when atoms react and form bonds what are they trying to do?

Answer 94

they try to achieve noble gas structure, they do this through either transferring electrons to each other ( ionic bond) or by sharing electrons with each other (covalent bond).

Hydrogen atoms only need two electrons in their outer level to reach the noble gas structure of helium. Once again, the covalent bond holds the two atoms together because the pair of electrons is attracted to both nuclei.

Question 95

what is an electrolyte?

Answer 95

electrolytes are substances which when dissolved break up into cations and anions.

Question 96

Good vs poor electrolytes?

Answer 96

covalent compounds that dissociate 100% in water, such as strin acids and strong bases, make good electrolytes. Other covalent compounds are usually poor electrolytes.
-IONIC COMPOUNDS THAT ARE SOLUBLE IN WATER ALWAYS MAKE GOOD ELECTROLYTES.

Question 97

what is a polar bond?

Answer 97

When two atoms are bonded together but one is way more electronegative than the other so it has more electron density. Like HF

Question 98

How do you think about ionic and covalent bonds that helps?

So what would be a bond that would exhibit the most ionic character if you could choose 2 atoms off the p table?

Answer 98

basically the larger the difference in electronegativity over 1.7 is going to give you an ionic. A bond between .5 and 1.7 will be polar covalent and something that is non polar covalent is below .5.

it would be the least electronegative element and the most electronegative element.

Question 99

How to tell if something has ionic character

Answer 99

All bonds that are not between two atoms of the same element have som ionic character. It is basically a measure of the polarity of the bond. Ionic species such as NACL have close to 100% ionic character.

Question 100

What is condosity?

If i have a 2M KCl solution what will expect the condosity to be?

Answer 100

Condosity is the concentration (Molarity) of an NaCl solution that will conduct electricity exactly as well as the solution in question.

Since K is more metallic than Na, we know that it is a better conductor. Therefore, the condosity will be something greater than 2.

Question 101

What is bond length

Answer 101

The distance between the nuclei of the atoms forming the bond.

Question 102

what is bond energy? do stable compounds have high or low bond energies?

Answer 102

The energy stored in the bond; the energy required to break the bond.

Stable compounds have high bond energies

Question 103

Does a high energy molecule have high bond energy?

Answer 103

No, a high energy molecule is unstable and requires very little energy to dissociate the bond.

Question 104

What is bond dissociation energy

Answer 104

Same thing as bond energy; the amount of energy required to break the bond.

Question 105

what is heat of combustion? And do high energy molecules or low energy molecules have a higher heat of combustion?

Answer 105

Amount of energy released when a molecule is combusted with oxygen. The higher the energy of the molecule (less stable) the higher the heat of combustion.

Question 106

why do bonds form? is energy required or released when a bond is formed?

Answer 106

Bonds form so the atoms can become more stable. Remember they want to be like those noble gases.

Bond formation makes the participants more stable so they loose energy. It is the same as you loosing energy and relaxing on your couch. It takes energy to break bonds

Question 107

why is the heat of combustion greatest for the most unstable molecules?

Answer 107

?

Question 108

what is a coordinate covalent bond?

Answer 108

this a covalent bond in which both electrons shared in the bond are donated by one atom. This atom must have a lone pair. If a molecule doesnt have a lone pair of electrons it CANNOT form coordinate covalent bonds with metals or other Lewis acids.

Question 109

describe what a mole is?

Answer 109

A mole is a unit of measurement. Its like a dozen. Lets say you have 1 mole of carbon this also means that you have 12.1 grams of carbon. This also means that you have 6.022*10^23 atoms of carbon

Question 110

whats the difference between molecular and empirical formula?

Answer 110

The empirical formula is just the ratio

Question 111

what does percent mass equal?

Answer 111

percent mass = (mass of one element/total mass of the compound) *(100%)

Question 112

what is the percent mass of carbon in glucose? (C6H12O6)

Answer 112

(72/180)*100 40%

Question 113

How do you derive a formula from percent mass?

Answer 113

1) change each percentage of each element into grams (15%=15g)
2) convert the grams of each element into moles by dividing by there molar mass
3) Look at the element with the lowest number of moles. Calculate approximately how many time it will divide into each of the other molar amounts for each of the other elements-this number will be the subscript for each element in the empirical formula. If the numbers aren’t to the lowest possibility divide it by a common denominator.

Question 114

Can you find the molecular formula if you have just been given percent mass of each element?

Answer 114

NO! An empirical formula is all you can get from percent mass alone. To get the molecular formula, you must be given the MW of the unknown compound.

Question 115

how do you name general ionic compounds? The nomenclature of inorganic is primarily the naming of ionic compounds.

Answer 115

Name the cation first, then the anion. ( Calcium sulfate is CaSO4)

Question 116

How do you name transition metals?

Answer 116

When written in words, compounds that include transition elements must have a Roman numeral showing the oxidation state of the metal ( iron(2)sulfate vs iron(3)sulfate)

Question 117

naming of monoatomic ions?

Answer 117

These are named by replacing the last syllable with -ide (chloride, sulfide, hydride)

Question 118

what is the formula for hydroxide?

Answer 118

OH -

Question 119

Nitrate?

Answer 119

NO3 -

Question 120

Nitrite?

Answer 120

NO2-

Question 121

Chlorate and Chlorite and Hypochlorite, Perchlorate

Answer 121

ClO3 - ClO2- ClO- ClO4 -

Question 122

Bicarbonate

Answer 122

HCO3-

Question 123

carbonate

Answer 123

CO2^3-

Question 124

ammonium

Answer 124

NH4+

Question 125

Sulfate

Answer 125

SO4^2-

Question 126

Phosphate

Answer 126

PO4^3-

Question 127

Permanganate

Answer 127

MnO4-

Question 128

Cyanide

Answer 128

CN-

Question 129

Manganite

Answer 129

MnO2-

Question 130

For acids if the ion name ends in -ate what should you replace it with?

Answer 130

-ic Like Nitrate would be Nitric

Question 131

For an acid if the ion name ends in ite what should you replace it with?

Answer 131

-ous as in Nitrite it would be Nitrous Acid

Question 132

For acids if the parent is a single ion rather than a polyatomic ion what should you do?

Answer 132

Replace the -ide ending with -ic and add Hydro at the beginning. as in Iodine this would be Hydroiodic acid.

Question 133

How do you name binary compounds?

Answer 133

Name the element furthest down and to the left on the p table first. Use poly prefix as necessary. ( Nitrogen Trioxide, Sulfur Dioxide). Some have common names such as ammonia and water.

Question 134

What is a combination reaction?

Answer 134

Combination- A synthesis reaction is when two or more simple compounds combine to form a more complicated one. These reactions come in the general form of: A + B —> AB

8 Fe + S8 —> 8 FeS

Question 135

What is a decomposition reaction?

Answer 135

Decomposition- A decomposition reaction is the opposite of a synthesis reaction - a complex molecule breaks down to make simpler ones. These reactions come in the general form:
AB —> A + B 2 H2O —> 2 H2 + O2

Question 136

What is a single displacement reaction?

Answer 136

Single displacement: This is when one element trades places with another element in a compound. These reactions come in the general form of:
A + BC —> AC + B Mg + 2 H2O —> Mg(OH)2 + H2

Question 137

What is a double displacement reaction ( aka metathesis reaction)

Answer 137

Double displacement: This is when the anions and cations of two different molecules switch places, forming two entirely different compounds. These reactions are in the general form:
AB + CD —> AD + CB Pb(NO3)2 + 2 KI —> PbI2 + 2 KNO3

Question 138

What are the steps to balancing equations?

Answer 138

1) balance the number of carbons
2) balance the number of hydrogens
3) balance the number of oxygens
4) balance any remaining atoms
5 if you need to you can multiply by decimals like 1.5 or something
6) if you do multiply by a decimal remember to go back in and multiply all the coefficients because you can have decimals as coefficients
7) make sure you check your work to see if both sides are balanced

Question 139

Le Cs principle

Answer 139

If, for example, you removed C as soon as it was formed, the position of equilibrium would move to the right to replace it. If you kept on removing it, the equilibrium position would keep on moving rightwards - turning this into a one-way reaction.

Question 140

What would happen if you changed the conditions by increasing the pressure?

Answer 140

According to Le Chatelier, the position of equilibrium will move in such a way as to counteract the change. That means that the position of equilibrium will move so that the pressure is reduced again.

Pressure is caused by gas molecules hitting the sides of their container. The more molecules you have in the container, the higher the pressure will be. The system can reduce the pressure by reacting in such a way as to produce fewer molecules.

Question 141

What would happen if you changed the conditions by decreasing the pressure?

A+2B—– C+D

Answer 141

The equilibrium will move in such a way that the pressure increases again. It can do that by producing more molecules. In this case, the position of equilibrium will move towards the left-hand side of the reaction.

Question 142

What happens if there are the same number of molecules on both sides of the equilibrium reaction?

Answer 142

In this case, increasing the pressure has no effect whatsoever on the position of the equilibrium. Because you have the same numbers of molecules on both sides, the equilibrium can’t move in any way that will reduce the pressure again.

Question 143

What would happen if you changed the conditions by decreasing the temperature?

A + 2B —– C + D forward reaction is exothermic deltH= -250

Answer 143

Suppose the system is in equilibrium at 500°C and you reduce the temperature to 400°C. The reaction will tend to heat itself up again to return to the original temperature. It can do that by favouring the exothermic reaction.

Question 144

Le C with temp

Answer 144

Increasing the temperature of a system in dynamic equilibrium favours the endothermic reaction. The system counteracts the change you have made by absorbing the extra heat.

Decreasing the temperature of a system in dynamic equilibrium favours the exothermic reaction. The system counteracts the change you have made by producing more heat.

Question 145

what is the atomic weight?

Answer 145

This is the average of the atomic masses of the different isotopes. Like carbon 12 and Carbon 14 ect. This is the number that refers to grams per mole.

Question 146

What is the molecular weight?

Answer 146

This is like atomic weight but is now a molecule. So you would add up each individual atomic mass in that molecule.

Question 147

what is the molar mass?

Answer 147

The molar mass is the mass of one mole of something. This can relate to atoms and molecules. So for carbon 1 mole of a cabon weighs 12g. Or 1 mole of CO weights 28 grams.

Question 148

What is Avogardos number?

Answer 148

This is 6.02210^23. This number refers to how many molecules, ions, atoms ect. So if we have 1 mole of carbon this means that we have 6.02210^23 carbon atoms. And the weight of that is 12 grams. Same goes for molecules if we have one mole of CO we have that many molecules of CO and that many molecules has a mass of 28 grams.

Question 149

What is molarity?

Answer 149

Molarity = moles/L So if HCl and it has a molarity of 2.5. This means that for every liter there is 2.5 moles of HCl, or 2.5* 6.022*10^23 molecules of HCl

Question 150

If we have 1 mol of carbon, how many carbon atoms is that?

Answer 150

6.022*10^23

Question 151

If we have 1 mole of CO. how many grams does 1 mole of CO weigh?

Answer 151

28 grams

Question 152

If we are trying to solve for the limiting reagent, what are the steps?

Answer 152

The limiting reagent is the reagent that will run out first when a reaction occurs
1) Balance the equation
2) convert reagents (reactants) to moles
3) Compare the number of moles you have to the number of miles required to run one cycle of the reaction, as indicated by the coefficients.
Say you have C3H8 + 5O2 —– 3CO2 + 4H2O
we have 32 g of O2 and 11 g of C8H3
2) convert these to moles O2 = 1 mol and C8H3 = .25 mol
3) then you need to look at the balanced equation and say when C3H8 reacts with O2. Its a five to one ratio. So for every 1 mol or (6.022*10^23 molecules) of C3H8, 5 moles of O2 (or about 30 * 10^23) will react. So set it up as a conversion factor
you have .25 moles C8H3 (5 moles O2/ 1 mole C8H3) this will give you the amount of moles. Then compare this to the other mole values.

Question 153

Limiting reagent altius example.

Answer 153

combustion of methane CH4 + 2O2 —- CO2 + 2H2O

Suppose you have 1.5 moles of O2 and only 1.0 moles of methane. Because you need two moles of O2 to react with one mole of methane, you will run out of O2 first and it is therefor your limiting reagent. Even though you have more moles of O2 than you do of methane.

Question 154

What’s the definition of theoretical yield, actual yield, and percent yield?

Answer 154

The theoretical yield(in grams) of a reaction is the amount of product that would be formed if the reaction went to completion. You can solve for this by taking the amount of moles from the limiting reagent and converting this to grams using the final products molecular mass.
-Actual yield would be the actual amount in grams that you actually got when performing the experiment and weighing after you’re done with the experiment. You can then find the percent yield by taking the actual yield divided by the theoretical yield to find the percent yield to see how accurate you did the experiment.

Question 155

What are two ways that you can increase the yield of your experiment?

Answer 155

1) Start with more reactants
2) Shift the equilibrium to the right using one of the action of Le Chateliers principle. This includes one of the most common methods and that is removing products as they are formed. By doing so you force the reaction into a constant state of “catch up” and will continue to try and reach equilibrium.

Question 156

Will adding more reactants increase the overall quantity of the yield and the percent yield?

Answer 156

It will increase the overall quantity but not the percent yield. You must add more of the limiting reagent too in order to increase the overall quantity.

Question 157

When asked to predict the species that will require the most oxygen to combust what should you do?

Answer 157

Add 1.0 for each carbon and subtract 0.5 for each oxygen. The higher the resulting number the more oxygen necessary for full combustion. This is not NOT the actual number of moles required- it’s only a ranking system.

Question 158

Which requires the most oxygen to combust, propane, propanol, propanoic acid?

Answer 158

Propane

Question 159

Define equilibrium conceptually?

Answer 159

When the forward and reverse reaction are happening at equal rates. This doesn’t mean the concentrations on each side are equal however

Question 160

What’s equation for the equilibrium constant Keq? And are pure liquids and pure solids included in this equation?

Answer 160

Keq = (C)^c (D)^d / (A)^a (B)^b Each of these are raised to the coefficient which in front of each in the balanced equation.

No!

Question 161

How does each of the following effect equilibrium? Catalyst, increased temp, lowering the Ea, stabilizing the transition state, addition of reactants and products?

Answer 161

A catalyst will have no effect on equilibrium, besides speeds up the rate of a reaction reaching equilibrium, Lowering the Ea is basically the same thing as adding a catalyst, if you add products that will shift the equilibrium to the left and vice versa for addition to the reactants. Temperature will affect the equlibrium depending on if the reaction is endo or exothermic.

Question 162

Le Cs principle

Answer 162

The reaction will favor the side which relieves its stress. So if you have A+ B + heat — C+ D and you add heat it will move to the right to try and relieve that heat and find its way back to equilibrium

Question 163

When do you use the reaction quotient and the Keq?

If Q>K what does the mean?
If Q<K what does this mean?

Answer 163

You use the Keq when the reaction has already reached equilibrium. You use the Reaction Q equation when the reaction hasn’t reached equilibrium yet.

Q>K the reaction will proceed to the left meaning a higher concentration of products
Q<K the reaction will proceed to the right meaning there is a higher concentration in reactants

Question 164

Why aren’t covalent compounds good conductors?

Answer 164

Because the electrons in the outer most shell are shared by the other atom. Covalent compounds are only good conductors unless they are good electrolytes. Even then it’s the ions that are good conductors not the molecule itself.