Chemical Rxns

Question 1

When filling up an atom’s electrons into the energy levels/ shells, how should you go about it?

Answer 1

1. look at the atomic #= the number of protons , which in a neutral atom is equal to the number of electrons
2. look at the rows aka periods to see the number of energy levels/ shells
3. look at the columns aka the groups to see the number of valence electrons
4. place the said number of valence electrons into the outermost/ valence shell
5. fill in the other electrons into the electron levels/ shells via the 2, 8, 18, 32, 50 rule

Question 2

Valence electrons are found where? What do they participate in?

Answer 2

• in the outermost, valence shell
• they are the ones participating in the chemical bonds

Question 3

The number of valence electrons tells us what?

Answer 3

how the atom will react with other atoms

Question 4

What do all atoms strive to fullfill what rule? What does that rule dictate?

Answer 4

• octet rule
• the atom strives to have 8 electrons in its valence/ outermost shell through losing, gaining , or sharing the valence electrons , with the goal of becoming like its nearest noble gas

Question 5

What is the max electrons supported by each energy level (up to 5)?

Answer 5

1. 2
2. 8
3. 18
4. 32
5. 50

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Question 6

How do you find out how many bonds an atom will make?

Answer 6

easy: number in the ionic charges formed by the element

based on how many electrons are gained or lost to become its nearest noble gas (aka the way to get to its ionic charge)

Question 7

What is a chemical bond?

Answer 7

atoms gaining or losing or sharing valence electrons to satisy the octet rule, which is to get 8 electrons in the valence/ outermost shell of the atom to become like its nearest noble gas

Question 8

In general, what are the 3 types of chemical bonds?

Answer 8

• ionic
• covalent
• hydrogen

Question 9

Describe ionic bonds
* atoms that are involved do what?
* what type of elements form these bonds?
* explain the EN difference b/w the atoms invovled
* what are some examples (5)?

Answer 9

• atoms invovled will either gain or lose electrons (transfer of electrons from metal to nonmetal) to generate ions (anions or cations) that have a bond through just attraction b/w opposite charges
• b/w metal (less EN –> lose electrons to become a cation) and nonmetal (more EN –> gain electrons to become an anion)
• LARGE EN difference b/w atoms invovled

examples
* NaCl , NaBr, KCl
* MgO
* CaS

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Question 10

Describe covalent bonds
* atoms that are involved do what?
* what type of elements form these bonds?
* what are the 2 types of covalent bonds?
* what are some examples (general, polar, nonpolar)?

Answer 10

• atoms involved are sharing electrons (sometimes one atoms is more EN than the other, so attracts more e-‘s and is partially - and the other is partially +)
• b/w 2 nonmetals
• polar and nonpolar

Examples
* in general: CO2
* polar: HCl, OH, H2O (dipole moment pointing towards the more EN atom ie. O in H2O)
* nonpolar: diatomic mlcs and C-H bonds

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Question 11

Explain polar bonds (including what type of bond it is, including examples)

Answer 11

• a type of covalent bond where the EN difference b/w the two atoms are greater than or equal to 0.5 –> so there is an unequal sharing of electrons with one atom being more EN and attracting more electrons and being partially negative and other one being partially += forming a dipole moment, which points towards the more EN atom)

Examples
* HCl (H is partially +, Cl is partially -)
* OH (H is partially +, O is partially -)
* H2O (H is partially +, O is partially -)

Question 12

Explan nonpolar bonds (including what type of bond it is, including examples)

Answer 12

• a type of covalent bonds where the EN difference b/w the two atoms is less than 0.5 –> so there is an equal sharing of electrons

Examples
* diatomic mlcs and C-H bonds

Question 13

Describe hydrogen bonds
* what elements form these bonds?
* where are these bonds found?
* strength of them compared to ionic/ covalent bonds

Answer 13

• H-NOF
• found in H2O, proteins, nucleic acids (DNA); found within a single mlc OR b/w mlcs
• weaker than ionic and covalent bonds and are NON-covalent

Question 14

Chemical reactions are depicted by what?

Answer 14

chemical equations

Question 15

Describe chemical reactions
* what turns into what?
* what law does it follow?

Answer 15

• one or more substances turns into a completely new substance
• law of conservation of mass : DOES NOT create or destroy mass or the atoms –> which means the number of atoms aka the number of moles of element is the SAME on the reactants and products side

Question 16

What is the number of moles represented in in an equation

Answer 16

the coefficient before the element

Question 17

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Question 18

In general, what are the 5 types of chemical reactions?

Answer 18

• combination/ synthesis
• decomposition
• single displacement aka single replacement and single substitution
• double displacement aka double replacement and substition and precipitation rxn
• combustion

Question 19

Explain combination reaction (including what is another name for it)

Answer 19

• aka synthesis reaction
• 2 reactants combine to form 1 product (A + B –> AB) [ element + element –> cmpd]

Examples in ipad

Question 20

Explain decomposition reaction

Answer 20

• usually endergonic, so requires energy
• 1 reactant breaks down into 2 or more products (AB –> A + B) [ cmpd –> element + element]

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Question 21

Explain single displacement rxn (including what is another name for it)

Answer 21

• single replacement or single substitution rxn
• 1 reactant is replaced or displaced with another ( A + BC –> B + AC OR C + AB) [ element + cmpd –> element + cmpd]

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Question 22

Explain double displacement rxn (including what is another name for it)

Answer 22

• double replacement and substitution and precipitation rxn
• 2 compounds come together to form two other compounds with 2 element swapped; solid made is the precipitate ( AB + CD –> AD + CB) [ cmpd + cmpd –> cmpd + cmpd]

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Question 23

Explain a combustion reaction (including is it exo or endothermic)

Answer 23

a substance reactions with O2 to release energy (exothermic) as light and heat ( O2 + _____ –> CO2 + H2O)

Question 24

What are the factors that influence the rate of a reaction? Explain each

Answer 24

• catalyst : lowers the activation energy, which is the min energy to start a chemical reaction, which increases the rate of the reaction
• concentration : inc the conc of reactant = inc the number of collisions b/w them = inc rate of rxn
• temperature: inc the temp = inc the frequency and speed of collisions and also the KE of the reactants –> more fraction of reactants are able to reach the AE –> more reactants are able to complete the rxn
• pressure (only applies to gasesous atoms): inc pressure , increases the temperature = increases the OVERALL velocity of the particles –> inc the # if collisions –> inc rate of rxn
• SA: inc SA b/w reactants –> inc the # if collisions –> inc the rate of rxn

Question 25

What item are catalysts usually? What macromolecule is that item usually? Give an example of that item. Give one characteristic.

Answer 25

• enzymes
• proteins (end in -ase)
• amlyase turning amylose (starch) into maltose (simple sugar)

NOT consumed in a reaction

Question 26

Explain Le Chatelier’s Principle

Answer 26

• when a stressor is added to a system, will try to shift to offset the stressor or to restore the chemical equilibrium

Question 27

What are examples of stressors dictated by Le Chatelier’s Principle

Answer 27

• change in temp (inc or dec) (factor in endothermic = heat is reactant or exothermic (heat is product) (also inc in temp in general will inc the OVERALL velocity of the particles = inc the number of collisions = inc rate of reaction)
• change in concetration of reactions or products (inc or dec)
• change in pressure (only when dealing with gases and when there is an actual DIFF in moles of gas b/w reactants and products)- a inc in pressure shifts the reaction towards the side with less moles of gas and a dec in pressure shifts the reaction towards the side with more moles of gas

examples in ATI manual page 242 question 1 and 2.

Question 28

Extra:
What is a neutralization reaction?

Answer 28

• acid + base –> salt (ionic cmpd) + water

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Question 29

What subtance lowers the activation energy of a chemical reaction?

Answer 29

catalyst (most of the time an enzyme, which are usually proteins)

Question 30

An enzyme does what to a chemical reaction?

Answer 30

speed up the forward AND reverse reaction

Question 31

Extra:
What is a redox reaction?

Answer 31

OIL RIG
* oxidation has electrons as product and reduction has electrons as reactant

Question 32

What are two elements that DO NOT follow the octet rule? Instead what rule do they follow? What does that rule say?

Answer 32

• H and He
• DUET rule
• need 2 electrons in valence/ outer shell instead of 8.

Question 33

What elements should be balanced last?

Answer 33

O and H