What is the percent of copper in the 0.0125 moles of copper (ii) sulfate?

Answer 1

% Cu = g Cu / g CuSO4 (x100%)

molar mass CuSO4 = 159.6 g/mol

atomic mass Cu = 63.5 g/mol

% Cu = 63.5 g / 159.6 g (x100%) = 39.8% Cu

This is the % Cu in 0.0125 moles or 125 moles or 12500 moles of CuSO4. The % composition doesn't change with different amounts of the substance.

If you wanted to know the mass of Cu in 0.0125 moles of CuSO4, that's a different story.

mass of 0.0125 mol CuSO4 = 0.0125 mol x 159.6 g/mol = 1.995 g

mass Cu = 1.995 g CuSO4 x 39.8% = 0.794 g Cu