Chemical Calculations With Moles

Question 1

What is the yield of a reaction?

Answer 1

mass of product obtained from the reaction

Question 2

What is the theoretical yield of a reaction?

Answer 2

maximum mass of the product that could have been produced

Question 3

Why is the actual yield always less than the theoretical yield?

Answer 3

• reaction may be reversible
• some of the product can be lost on separation
• unexpected side reactions between reactants

Question 4

What is the percentage yield?

Answer 4

actual yield as a proportion of theoretical yield

Question 5

How is percentage yield calculated?

Answer 5

(actual yield/theoretical yield) x 100

Question 6

What is atom economy?

Answer 6

measure of how many atoms of the reactants end up as useful products

Question 7

Why is a high atom economy desirable?

Answer 7

results in less waste/ is more sustainable

Question 8

How is percentage atom economy calculated?

Answer 8

(Mr of useful product/Mr of all products) x 100

Question 9

How can concentration in mol/dm^3 be calculated?

Answer 9

moles of solute/volume

Question 10

What is a titration?

Answer 10

method used to calculate the concentration of an unknown solution

Question 11

What is the end-point?

Answer 11

the point at which the reaction is complete and no substance is in excess

Question 12

How should solution be added from the burette close to the end-point?

Answer 12

drop by drop, swirling in between

Question 13

Why is a white tile used in titration?

Answer 13

to see the colour change better

Question 14

What is a titre?

Answer 14

volume of solution added from the burette

Question 15

What are concordant titres?

Answer 15

titres within 0.1cm^3 of each other

Question 16

What volume does one mole of any gas occupy at room temperature and pressure?

Answer 16

24dm^3 or 24000cm^3