2.1 atoms and reactions

Question 1

what is relative atomic mass

Answer 1

Weighted mean mass of an atom of an element compared to 1/12th the mass of an atom of carbon-12 which is taken to be exactly 12.
Has no units
Are a comparison between the element and carbon-12
Not a direct measure of mass of an atom.
Hydrogen- lightest so mass=1
Lithium is 7 time heavier so mass=7

Relative atomic mass= (isotopic mass * abundance)
100

Question 2

what is relative isotopic mass

Answer 2

Mass of an atom of an isotope of the element compared to 1/12th of the mass of an atom of carbon-12

Question 3

what is relative molecular mass

Answer 3

Weighted mean mass of a molecule of the compound compared to 1/12th of the mass of an atom of carbon-12

Question 4

what is relative formula mass

Answer 4

Weighted mean mass of a formula unit compared to 1/12th of the mass of an atom of carbon-12

Question 5

what is mass spec

Answer 5

The mass spectrum of an element shows a peak for each isotope of that element. The mass corresponding to each peak, together with their relative abundance can be used to calculate the relative atomic mass.

Question 6

what does show mass spectra

Answer 6

The mass spectrum shows multiple peaks, the one with the largest m/z value, the molecular ion shows the relative molecular mass of that molecule.
The rest of the peaks show fragment ions formed when the molecule breaks up. Molecules break up more readily at weak bonds or bonds that give rise to fragments that are more stable.
Abundance against mass/charge
The peak number= number of isotopes.

Question 7

what is the process that comes with mass spectrometry

Answer 7

The sample is bombarded with electrons (produces an ion).
The ion is accelerated by an electric field
The ion passes through a magnetic field to deflect.
Higher mass means less deflection.
A sensor detects and records the ions reaching it

Question 8

what is meant by empirical formula

Answer 8

The simplestwhole number ratio of various atoms present in a compound.
Eg. The empirical formula of C2H6 is CH3

Question 9

what is meant by molecular formula

Answer 9

Shows the exact number of different types of atoms present in a molecule of a compound.

Question 10

what is moles

Answer 10

amount of substance that contains as many elemental particles as there are atoms in exactly 12g of12C

Question 11

what is percentage yield

Answer 11

amount of reactant that is successfully converted into product is known as the yield.

% yield= actual yield X 100
theoretical yield

Question 12

what is atom economy

Answer 12

Useful for industry as it shows waste product.
Can be improved by finding uses for the waste products, thus making it more sustainable

Mr of desired product X100
Mr of actual product

Question 13

what is the laws that determine the ideal gas equation

Answer 13

Boyles law tells us volume is indirectly proportional to pressure. Higher pressure= lower volume
Charles’ law tells us volume is directly proportional to pressure. Higher temp= higher volume
Avogadro’s law tells us higher moles= higher volume

Question 14

what are ideal gases

Answer 14

Molecules in random motion
No intermolecular forces present
Elasticcollisionswithno exchange of kinetic energy
Particles of 0 volume

Question 15

how did the ideal gas equation get worked out

Answer 15

Real gases don’t follow these conditions exactly but do get close at high temperatures or low pressures.
All gas equations assume they do.
Volume of gas is directly linked toAvogadro’slaw, Charles’ law and Boyles’ law.
Combining these give either V∝n(T/P) orPV∝nT. By adding a constant of proportionality, which is known as the gas constant (R), you get the gas constant equation.

Question 16

what is the ideal gas equation

Answer 16

Idea gas equation= P×V=n×R×T

n- moles, p- pressure, r- constant (8.413), V- volume, T- temp
Standard equations should use Pa and m3
1KPa= 1×103
1dm3= 1×10-3m3
Value of R is calculated at standard conditions to give
8.314 JMol-1K-1

Question 17

what is dilution

Answer 17

Dilution = original concentration
Diluted concentration
Once the dilution has been calculated, the volume of the original stock that is required can be determined.
Remaining volume is given with distilled water.
Original stock volume= total volume needed
Dilution

Question 18

what is standard solution

Answer 18

A standard solution is a solution with a known concentration.

Question 19

how do you make a standard solution

Answer 19

1. Dissolve the solute in a small amount of distilled water.
2. If dissolved in a beaker, transfer to volumetric flask.
3. Rinse the beaker with more distilled water and add to the flask to minimize residue left behind.
4. Fill volumetric flask with distilled water till meniscus reaches the etch mark on the flasks neck.
5. Ensure the etch mark is level with your eye.

Question 20

what is concentration

Answer 20

The concentration of a solution is a measure of the amount of solute dissolved within a volume of solvent.
Moles = concentration × volume.

Question 21

what is the difference between solvent and solute

Answer 21

Solute- substance that has been dissolved

Solvent- substance other chemicals dissolve in, usually water.

Question 22

what are acids

Answer 22

Is a chemical that releases a hydrogen ion (H+), referred to as protons when dissolved in water.
Therefore is a proton donor and dissociates into it’s ions in water

Question 23

what are the common acids

Answer 23

Hydrochloric acid- HCl
Nitric acid- HNO3
Ethanoic acid- CH3COOH
Sulfuric acid- H2SO4
Phosphoric acid- H2PO4

Question 24

what are strong acids

Answer 24

Strong acids completely dissociates in water to release H+

At the same concentration, a stronger acid has a higher amount of protons released than a weak acid

Question 25

what are weak acids

Answer 25

Weak acids partially dissociates in water to release some H+.

Question 26

what are bases

Answer 26

Is a chemical that reacts with protons released by acids

Therefore is a proton acceptor

Question 27

what are common bases

Answer 27

Metal oxides
Hydroxides

Alkali refer to soluble bases that release hydroxide ions (OH-) when they dissolve in water

Question 28

what is ammonia

Answer 28

Is an alkali because when it dissociates it will react with water, generating ammonium ( NH4+).

Question 29

what is salts

Answer 29

Acids react to form salts, an ionic compound formed when the H of an atom is replaced with a metal ion.

Question 30

what is acid reactions

Answer 30

Acid + base → salt + water
Acid + alkali → salt + water
Acid + carbonate → salt + water + carbon dioxide
Acid + metal → salt + hydrogen
Ammonia forms ammonium ions so its salts are referred to as ammonium salts

Question 31

what is water important for

Answer 31

Is an important for acid and alkali formation as H+ ions and OH- ions can only be formed in solution

Question 32

what oxidation number

Answer 32

Shows the charge on an tom if all of its bonds are considered to be totally ionic.

Question 33

what is the priority of oxidation states

Answer 33

Elements in their natural state = 0
Total oxidation states in a molecule= 0
Total oxidation state in an ion= charge 
Oxidation increases the x=oxidation state 
Reduction decreases the oxidation state

Question 34

what is redox reactions

Answer 34

Involves the transfer of electrons, resulting in both oxidation and reduction of atoms.

Question 35

what is disproportionation reactions

Answer 35

Where an element has been both oxidised and reduced