Paper 1/2

Question 1

Calculating relative formula mass

Mr

Answer 1

Sum of Ar (atomic masses) of all atoms in a compound or molecule.

Question 2

Calculating limiting reactant

Answer 2

1) balance the symbol equation
2) calculate the moles of each substance
3) find molar ratio
4) calculate number of molecules used in reaction - reason for balancing
5) state limiting reactant.

Question 3

Calculating limiting reactant

Answer 3

1) balance the symbol equation
2) calculate the moles of each substance
3) find molar ratio
4) calculate number of molecules used in reaction - reason for balancing
5) state limiting reactant.

Question 4

Calculate molecular formula from empirical formula

Answer 4

1) find Ar of each element
2) calculate Mr of empirical formula
3) divide molecular formula Mr by empirical formula Ar
4) times formula by value to get molecular formula

Question 5

Calculate theoretical yield

Answer 5

1) underline substances in equation questioned.
2) calculate Mr of substances
3) find mass made by 1g of reactant
4) x mass by mass of reactant in question.

Question 6

Calculating the number of particles

Answer 6

Number of particles = moles x avegadro constant.

6.02 x 10(23)

Question 7

Calculate molar gas ratio

Answer 7

Molar volume = 24dm(3)

Volume = moles x molar volume.

Question 8

Calculate empirical formula from mass

Answer 8

1) find Ar of each element
2) divide mass of each element by its Ar
3) divide the answers by smallest value to find ratio
4) write out empirical formula

Question 9

Calculate relative formula mass from relative mass and abundance of isotopes.

Answer 9

Total mass of atoms ÷ number of atoms (100)

Question 10

Calculate concentration from moles

Answer 10

Conc = mole ÷ volume

Volume in dm(3) = cm(3) ÷ 1000

Question 11

Calculating mass of reactants or products

Answer 11

1) Underline substance of given mass and substance you are finding.
2) find Mr for each substance
3) work out molar ratio
4) divide Mr of unknown mass of Mr of known mass

Question 12

Calculating converting conc in gdm(-3) to mol dm(-3)

Answer 12

Conc mol dm(-3) = conc in gdm3 ÷ mr of solute

Question 13

Calculate concentration from mass

Answer 13

Concentration = mass ÷ volume

Question 14

How to calculate Rf

Answer 14

Distance moved by solute ÷ distance moved by solvent

Question 15

Calculate percentage yeild

Answer 15

Actual yield ÷ theoretical yield, x100

Question 16

Calculating moles

Answer 16

Moles = mass ÷ Mr

Question 17

Calculating mass

Answer 17

Mass = Mr x moles

Question 18

Calculating bond energies

Answer 18

• Draw structural formula
• calculate energy to break bonds
• calculate energy out during bond formation
• calculate energy difference - exo and endo

Question 19

Titration calculations

Answer 19

• Write out balanced equations
• Underline reactants needed
• Deduce molar ratio
• Convert volume to dm(-3)
• Draw table and substitute values
• Find moles and known conc
• Use molar ratio to find moles of unknown substance
• Substitute values into table
• Find conc of unknown substance

Question 20

Deduce balanced equations from mass

Answer 20

• Find number of moles of substances with known masses
• Divide by smallest value
• Write formulale and known balanced number
• Finish balancing equations

Question 21

Calculate atom economy

Answer 21

Mr of desired product - Mr of sum of all reactants. X100