Moles

Question 0

RAM

Answer 0

Relative atomic mass/Ar

Question 1

(Sq 24) Mg
(Sq 25) Mg
(Sq 26) Mg
These are all … Of eachother ad they have more/ less …

Answer 1

Isotopes

Neutrons

Question 2

RAM is the … Of one mole of atoms compared to the mass of one mole of … Which is the most common isotope of … Which is the most common … On earth

Answer 2

Mass
Carbon-12
Carbon
Element

Question 3

RAMs are found on an element in the periodic table at the

Answer 3

Top left hand number in the element box

Question 4

Find the RAM of (sq35) Cl 75% and (sq37) Cl 25%

Answer 4

Total mass of 100 atoms: (75 x 35) + (25 x 37) = 3550
3550/100
Average Mass of one atom = 35.5

Question 5

RFM

Answer 5

Relative formula mass/Mr

Question 6

RFM is the … Of compounds can be measured on the same … Scale as elements

Answer 6

Masses

Carbon-12

Question 7

To calculate the RFM of a compound, the RAM of the individual elements are added together eg for H2O

Answer 7

Mr = (2 x H) + (1 x O)
(2 x 1) + (1 x 16)
Mr = 18

Question 8

Volume of gas equation

Answer 8

Volume = moles x 24

Question 9

Empirical formula is the … Ratio of the atoms in a compound eg hydrogen peroxide H2O2

Answer 9

Simplest

HO

Question 10

The empirical formula can be calculated from the mass of each element in a compound there are three stages to this process:

Answer 10

1) determination of mads or percentage of elements
2) divide the given mass or percentage by their RAM
3) calculate the ratio of atoms by dividing by the smallest value

Question 11

Find empirical formula for calcium bromide

Answer 11

Ca 20%/40(RAM) Br 80%/80(RAM)
Ca 0.5/0.5 Br 1/0.5
= 1 : 2
= CaBr2

Question 12

Equation for mass of a mole

Answer 12

Mass = Mr x moles

Can be rearranged

Question 13

Find the mass of two moles of air

Answer 13

[(78 x 28) + (22 x 32) /100] x 2 = 57.76g

Question 14

Find the mass of 1 mole of lead (II) nitrate Pb(NO3)2

Answer 14

207 + (2 x14) + (6 x 16) = 331g

Question 15

Find the molecular formula from the empirical formula of CH2

Answer 15

CH2 has a Mr of 14 (RAMs H=1; C=12)
All you need to find out is how many times 14 goes into eg 56. 56/14=4 so all you need is 4 lots of CH2. Finally the molecular formula is C4H8

Question 16

Reacting masses (the 4 steps)
What mass of ammonium nitrate fertiliser can be made from 18.9g of nitric acid

Answer 16

1) calculate the Mr of known substance (HNO3) Mr = 1.0 + 14.0 + (3 x 16.0) = 63.0
2) calculate the number of moles of known substance (HNO3)
3) calculate the number of moles required substance required substance (NH4NO3) from equation
4) calculate mass of required substance (NH4NO3) Mr= 80, mass= 0.30 x 80.0 = 24g

Question 17

Work out the percentage yield when 10g of ‘a’ would give 12.5g of product but you would only get 11.2g

Answer 17

(11.2/12.5) x 100 = 89.6%