Example 1:

Copper(II) carbonate decomposes to obtain copper(II) oxide. What is the theoretical yield of copper (II) oxide obtainable from 5.78g of copper(II) carbonate?

Answer:

The reaction takes place according to the equation \[CuCO_3 \rightarrow CuO+CO_2\]

When considering the theoretical yield, we imagine how much product we would have if all of the copper carbonate reacted completely to form copper oxide and carbon dioxide only. That would mean that one mole of copper carbonate woudl produce one mole of copper oxide and one mole of carbon dioxide.

The molecular mass of copper carbonate is 123.5 \(g \text{ } mol^{-1}.\)

Find the number of moles of copper carbonate: \[Moles = \frac{Mass}{\text{Molecular mass}}\]\[Moles = \frac{5.78}{123.5} = 0.0468mol\]

So, in theory, we should obtain 0.0468mol of copper oxide and 0.0468mol of carbon dioxide from our reaction.

The molecular mass of copper oxide is 79.5g.

Therefore, the theoretical yield of copper(II) oxide is: \[Mass = Moles \times \text{Molecular mass}\]\[\text{Mass of copper oxide} = 0.0468 \times 79.5 = 2.97g\]