# What mass of copper can be displaced by an excess of magnesium from a solution of copper chloride2

**What mass of copper can be displaced by an excess of magnesium from a solution of copper chloride2 weighing 268 g rram with a mass fraction of salt of 10%.**

1.Let’s find the mass of copper (II) chloride in solution.

Mass fraction of a substance is calculated by the formula:

W = m (substance): m (solution) × 100%,

m (substance) = (m (solution) × W): 100%,

m (substance) = (268 g × 10%): 100% = 26.8 g.

2.Let’s find the amount of copper chloride substance by the formula:

n = m: M.

M (CuCl2) = 64 + 71 = 135 g / mol.

n = 26.8 g: 134 g / mol = 0.198 mol.

3. Let’s compose the reaction equation, find the quantitative ratios of substances.

CuCl2 + Mg = MgCl2 + Cu ↓.

According to the reaction equation, 1 mol of copper chloride accounts for 1 mol of copper. The substances are in quantitative ratios of 1: 1.

The amount of copper and copper chloride will be equal.

n (CuCl2) = n (Cu) = 0.2 mol.

4. Let’s find the mass Cu.

m = n M.

M (Cu) = 64 g / mol.

m = 0.198 mol × 64 g / mol = 12.67 g.

Answer: m = 12.67 g.