The Mole and Avogadro

Question 1

How do you work out the moles if you know the volume and the concentration of something?

Answer 1

Moles= concentration x volume/1000

Question 2

What is the Avogadro constant number?

Answer 2

6.02 x 10^23

Question 3

How many grams are in 1 ton?

Answer 3

1,000,000 g

Question 4

How many grams in 1 kg?

Answer 4

1,000 g

Question 5

How many grams in 1 mg?

Answer 5

0.001 g

Question 6

How many moles are there in 72.0 g of Mg?

Answer 6

n=m/Mr

n= 72.0/ 24.3

n= 2.96 mol

Question 7

Calculate the number of moles of CO2 molecules in 11.0 grams of carbon dioxide.

Answer 7

n= m/Mr

n= 11.0/ ( 12+(16x2) )

n= 11.0/44

n= 0.25 mol

Question 8

Calculate the amount, in moles, of HCl in 33.2 cm^3 of 0.150 mol dm^-3 hydrochloride acid.

Answer 8

n=c x v/1000

n= 0.150 x 33.2/1000

n= 0.00498 mol

Question 9

How do you work out the moles if you know the mass of something?

Answer 9

Moles= mass (g) / Mr

Question 10

Why might you not get all the expected amount of product in a chemical reaction?

Answer 10

1) The reaction maybe reversible.
2) Some of the product may be lost when separated from the reaction mixture.
3) Some of the reactants may react in other reactions.

Question 11

How do you work out percentage yield?

Answer 11

% yield= mass of actual product obtained / mass of theoretical product x100