Question

In the balanced equation Cu + 2 HCl --> CuCl2 + H2, if you start with 0.15mol Cu and 0.38mol HCl, how many moles of HCl are left over (which means unused)?

Answer 1

This problem is providing a chemical reaction between 0.15 mol of copper and 0.38 mol of HCl and asks for the moles of HCl that are left over. At the end, the answer turns out to be 0.08 mol.

Uses of stoichiometry

In chemistry, we define stoichiometry as a tool allowing to calculate mole-mass or mole-mole relationships between different species involved in a chemical reactions.

In this case, for 0.15 mol of copper and 0.38 mol of HCl one can apply a mole ratio in order to calculate the moles of HCl consumed by the former, considering the 1:2 mole ratio between them:

$0.15 molCu*\frac{2mol HCl}{1molCu} \\\\=0.30 mol HCl$

This means that if 0.30 moles of HCl react and 0.38 moles are available, there is a left over or unused moles of:

$leftover=0.38mol-0.30mol\\\\leftover=0.08mol$

Learn more about stoichiometry: brainly.com/question/9743981