C4

Question 1

What does Mr stand for

Answer 1

Relative formula mass

Question 2

How to work out Mr

Answer 2

Add all Ar together

Question 3

What is a mole

Answer 3

Mr or Ar in grams, the relative atomic mass of carbon in grams is a mole (12g)

Question 4

What is Avogadros constant

Answer 4

6.02 x 10^23 - amount of atoms, molecules or ions in a mole

Question 5

Equation for moles

Answer 5

Mass(g)/Mr

Question 6

What does in excess mean

Answer 6

When the reaction stops, one reactant will still have some product that is unreacted

Question 7

What is the limiting reactant

Answer 7

The reactant that causes the reaction to stop, it gets used up first

Question 8

What is the yield of a reaction

Answer 8

Mass of product a reaction produces

Question 9

What is a percentage yield

Answer 9

Mass of product actually produced compared to the total mass of product that could be produced

Question 10

How to work out percentage yield

Answer 10

Mass of product produced/ maximum theoretical mass of products x 100

Question 11

Factors that effect percentage yield

Answer 11

• if reaction is reversible, products may begin to reform reactants
• may produce unwanted or unexpected products
• some reactants may be lost in handling or on equipment

Question 12

What is atom economy

Answer 12

Measure of the extent to which the atoms in the reactants end up in the desired products

Question 13

How to calculate atom economy

Answer 13

Mr of desired product/ Mr of total reactants x 100

Question 14

Calculating concentration with dm^3

Answer 14

Amount of solute (g)/ volume of solution (dm^3)

Question 15

Units of concentration

Answer 15

g/dm^3

Question 16

Calculation for concentration in cm^3

Answer 16

Mass of solute (g)/ volume of solution (cm^3) x 1000

Question 17

Titration method

Answer 17

1. Use the pipette and pipette filler to add 25 cm3 of alkali to a clean conical flask. Before doing this wash the pipette with distilled water
2. Add a few drops of indicator
3. Wash a Burkett e with distilled water, add a small amount of acid and allow it to run through the tap then fill with acid and note the starting volume
4. Slowly add the acid from the burette to the alkali in the conical flask, swirling to mix
5. Stop adding the acid when the end-point is reached (when the indicator first permanently changes colour). Note the final volume reading.
6. Repeat steps 1 to 5 until you get concordant titres

Question 18

What does concordat mean

Answer 18

Results within 0.1 cm^3

Question 19

Aims of titration

Answer 19

• volume of acid and alkali needed to react together
• concentration of one of the solutions