Calculations

Question 1

Rf Value (chromatography)

Answer 1

Distance travelled by solute / distance travelled by solvent

Question 2

Moles (3 equations)

Answer 2

Moles = Mass/Mr
OR
Moles = Volume (dmcubed) / Molar Gas Volume (Dmcubed /mol)

Question 3

Molar gas volume

Answer 3

Volume dmcubed / 24 dmcubed

Question 4

Concentration (g/dmcubed)

Answer 4

Mass of solute / volume

Question 5

Concentration (mol/dmcubed)

Answer 5

Moles / Volume

Question 6

Equation to change from mol/dmcubed to g/dm cubed

Answer 6

Conc in g/dm cubed = Mr x Conc in mol/dmcubed

(rearrange)

Question 7

Convert from cmcubed to dm cubed

Answer 7

divide by 1000

Question 8

Atom economy

Answer 8

(Mass of desired product / Total mass of products) x 100
INCLUDE BIG NUMBERS
Unit: %

Question 9

Number of particles

Answer 9

Moles x (6.02 x 10^23)

Question 10

Percentage Yield

Answer 10

(Actual Yield / Theoretical Yield) x 100

Unit: %

Question 11

What is Avogadro’s Constant?

Answer 11

6.02 x 10^23

Question 12

g to kg

Answer 12

divide by 1000

Question 13

State some reasons why the actual yield of a reaction is usually less than the
theoretical yield

Answer 13

• Some reactants may have remained unreacted
• Some product is lost during the reaction
• Side reactions occur
• Impurities in reactants