Moles

Question 1

Mole

Answer 1

The amount of substance containing as many particles as there are C atoms in exactly 12g of C – 12

Question 2

Avogadros constant

Answer 2

The number of particles per mole of a substance (6.02 x 10 23)

Question 3

Molar mass

Answer 3

The mass per mole of a substance (gmol-1)

Question 4

(Molecules/atoms/ions…interchangeable)
Particles =

Answer 4

Moles x Na (avogadro)

Question 5

Moles (solid)

Answer 5

Mass/Mr

Question 6

Moles (gas)

Answer 6

V/24
dm3

Question 7

Cm3 -> dm3

Answer 7

/1000

Question 8

Moles (solution)

Answer 8

c x v
(Dm3)

Question 9

Molar gas volume (rule)

Answer 9

One mole of any gas occupies a volume of 24 dm3 at RTP and has a molar gas volume of 24.0dm3mol-1

Question 10

Solution

Answer 10

Substances dissolved in a specific volume of water (solute in solvent )

Question 11

Stoichiometry

Answer 11

Reacting molar ratios
(Numbers in balanced equation)

Question 12

Atom Economy

Answer 12

Measure of the proportion of reactant atoms that become part of the desired product in the balanced chemical equation

Mr desired product/Total product Mr. (x100)

Question 13

Addition reaction atom economy

Answer 13

Always 100% (add to 1 compound)

Question 14

Benefits of high atom economy

Answer 14

-low waste - expensive to separate + dispose + environment effects
-reactants expensive
-limited raw materials - sustainability
-some catalysts developed to increase AE.

Question 15

% yield

Answer 15

% To indicate how much product is made in reaction compared to how much could have been made
Actual/theoretical (x100)

Question 16

Water of crystallisation

Answer 16

Water molecules that are bonded into the
crystalline structure of a hydrated compound, giving the compound a crystalline appearance

Question 17

Hydrated

Answer 17

When water of crystallisation is present in a crystal compound
(H2O joined to ionic compound so (CuSO4.xH2O)

Question 18

Opposite of hydrated

Answer 18

Anhydrous

Question 19

Empirical formula

Answer 19

The simplest whole number ratio of atoms of each element present the compound

Question 20

Empirical formula method

Answer 20

1) divide % or mass by Mr
2) divide by smallest number (ratio)
3) x to make whole numbers
4) formula

Question 21

Molecular formula

Answer 21

The actual number of atoms of each element in a molecule

Question 22

Molecular formula method

Answer 22

1) empirical formula
2) find Mr of each using empirical (empirical mass)
3) molar mass/ empirical mass
4) multiply empirical by answers

Question 23

How is Mr found

Answer 23

Mass spectroscopy machine
(= to molecular ion peak furthest to the right)

Question 24

% of water crystallisation

Answer 24

Mr atoms of element/Mr compound (x100)

Question 25

Formula from water of crystallisation

Answer 25

1) %/mass
2/ find moles
3) molar ratio
4) formula

Question 26

Experimental determination of water moles

Answer 26

1) measure mass of hydrated salt
2) heat - evapourate h20 attached
3) measure new mass = anhydrous salt
4) mass lost = water mass
5) find moles of each
6) ratio -> formula of hydrated salt

Question 27

Balancing combustion equation

Answer 27

1) balance c
2) h
3) o

Question 28

Reheating to constant mass

Answer 28

1)Mass of empty Crucible
2) mass of salt plus Crucible
3) add loose lid (prevent loss of solid, allow water vapour loss)
4) cool + reweigh
5) reheat + re weigh
6) repeat to constant mass
All water has been removed
Mass= anhydrous salt

Question 29

Conservation of mass

Answer 29

Mass equal before and after reaction
So can be used to find unknown elements, use Mr of known, find moles, find Mr unknown

Question 30

rule when scaling moles

Answer 30

moles decrease by same proportion as volume

Question 31

scaling concentration

Answer 31

1. find moles from original solution
2. n/v (new diluted volume) to find c of dilute solution

Question 32

steps to find the concentration of a given ion in a mixture using moles

Answer 32

1. find the total moles of each solution, n
2. for each compound: n x the number of [x] ion present in the compound
3. add the moles of the ion found above
4. use total volume of mixture + total moles of [x] ion in c=n/v

Question 33

how to identify the limiting reactant from volumes

Answer 33

test quantities of each reacted using using molar ratios

Question 34

if asked to find total gas volume after a given reaction where not all reactant gas is used up, remember to consider…?

Answer 34

any product gases - add to final vol