Question

A 1.225 g sample mixture of lithium hydrogen carbonate is decomposed by heating to produce 0.660 g lithium carbonate. Calculate the theoretical yield and percent yield of Li2CO3

Answer 1

Answer:

• The theoretical yield of lithium carbonate = 0.6659 g.

• The percent yield = 99.11%.

Explanation:

• Lithium hydrogen carbonate is decomposed by heating according to:

2LiHCO₃(s) → Li₂CO₃(s) + H₂CO₃(g).

It is clear that 2.0 moles of lithium hydrogen carbonate produce 1.0 mole of lithium carbonate.

• We need to calculate the no. of moles of (1.225 g) lithium hydrogen carbonate decomposed:

no. of moles of lithium hydrogen carbonate = mass/molar mass = (1.225 g)/(67.96 g/mol) = 0.018 mol.

• 0.02 mol of lithium hydrogen carbonate is decomposed to produce (0.02 mo /2 = 0.009 mol) of lithium carbonate.

∴ The theoretical yield of lithium carbonate = no. of moles x molar mass = (0.009 mol)(73.89 g/mol) = 0.6659 g.

∵ The percent yield = (actual yield/theoretical yield) x 100 = (0.660 g / 0.6659 g) x 100 = 99.11%.