Dimensional analysis format

Question

When 1.1 g of black copper (II) oxide Is mixed with an of hydrochloric acid the solution turns clear green, indicating the formation of copper (II) chloride. How many grams of copper (II) chloride form from this double replacement reaction?

Answer 1

To solve this problem, let's assume that all the copper (II) is converted from copper (II) oxide to copper (II) chloride. This means that the number of moles of copper (II) chloride and oxide are going to be equal. Now that we know this, we can use the molar masses of the two compounds to convert between the masses of the reactants and the products as follows:

Molar mass copper (II) oxide: 79.545 g/mol

Molar mass copper (II) chloride: 134.45 g/mol

1.1 g CuO * (1 mol CuO / 79.545 g CuO) = 0.01382865045 mol CuO

0.01382865045 mol CuO * (1 mol CuCl₂ / 1 mol CuO) = 0.01382865045 mol CuCl₂

0.01382865045 mol CuCl₂ * (134.45 g CuCl₂ / 1 mol CuCl₂ ) = 1.859262053 g CuCl₂

With these conversion calculations, all the units cancelled out to give us our desired product of 1.859262053 g CuCl₂, or ~ 1.9 g CuCl₂ when considering significant digits.

Final Answer: ~ 1.9 g CuCl₂