3.1 Chemical Measurements Questions

Question 1

The equation for the reaction of copper carbonate and sulfuric acid is:

CuCO3 + H2SO4 → CuSO4 + H2O + CO2

Relative formula masses : CuCO3 = 123.5; H2SO4 = 98.0; CuSO4 = 159.5

Calculate the percentage atom economy for making copper sulphate from copper carbonate.

Answer 1

123.5 + 98.0 = 221.5 for the reactants

CuSO4=159,5

159.5/221.5 x 100 = 72.009

72.0%

So, I am calculating the total formula mass of the reactants

But I only care about the product, so I only look at the products formula mass

So I divide the formula mass of the product I want by the total of the reactants

Question 2

Carbon can react with oxygen to produce carbon monoxide (CO).

1) Calculate the relative formula mass of CO
Relative atomic masses C = 12; O = 16

2)Calculate the percentage by mass of carbon in carbon monoxide.

Answer 2

1) CO is one atom of oxygen and one atom of carbon, therefore 12+16=28

2) Mass of carbon in carbon monoxide, so we know the total mass is 28

Carbon has a mass of 12

12/28= 42.85
42.9%

Question 3

Relative atomic masses Cl = 35.5 Fe = 56.

1) Calculate the relative formula mass of iron chloride (FeCl3)

2) Calculate the percentage of iron in iron chloride

Answer 3

1) FeCl3 = one atom of iron and three atoms of chlorine

1x56 + 3(35.5)= 162.5

2) Iron = 56

56/162.5 x 100 = 34.46

34.46%