3.3 Yield & Atom Economy

A student made zinc chloride by reacting 15.0 g of zinc carbonate with hydrochloric acid.

ZnCO₃ + 2HCl →  ZnCl₂ + CO₂ + H₂O

The percentage yield of zinc chloride was 82.4%.

Calculate the mass of zinc chloride the student actually produced.

Relative atomic masses (A_r): C = 12    Zn = 65   O= 16    Cl = 35.5     H= 1

A student made magnesium oxide by reacting 2.4 g of magnesium with steam:

Mg (s) + H₂O (g)  → MgO (s) + H₂ (g)

She calculated the theoretical yield should be 4.0 g of magnesium oxide, but she only obtained 3.2 g.

What was the percentage yield for the experiment?

An equation for the reaction between copper(II) oxide and carbon is:

2CuO + C  → 2Cu + CO₂

What is the percentage atom economy for the reaction to produce copper metal?

Relative atomic masses (A_r):     C = 12        Cu = 64

Relative formula mass (M_r):       CuO = 80

Which of these is/are a factor(s) in choosing a reaction pathway?

	Atom economy	Percentage yield	Rate of reaction
A	✔
B	✔	✔
C		✔	✔
D	✔	✔	✔

Which of the following does not explain why the yield of a reaction may not be 100%?

Calcium oxide can be produced by heating calcium carbonate in a rotating kiln.

CaCO₃   →   CaO  +  CO₂

If 120 tonnes of calcium carbonate is heated in the kiln and 53 tonnes of calcium oxide are produced, what is the percentage yield?

Relative atomic masses (A_r): Ca = 40   C = 12   O= 16