Question

Determine the volume of a 0.800 M K2Cr2O7 solution required to completely react with 4.24 g of Cu.

Answer 1

Answer: The volume of solution required is 0.0275 L.

Explanation:

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

Given mass of copper = 4.24 g

Molar mass of copper = 63.55 g/mol

Putting values in above equation, we get:

$\text{Moles of copper}=\frac{4.24g}{63.55g/mol}=0.067mol$

The chemical equation for the reaction of potassium dichromate and copper follows:

$K_2Cr_2O_7+3Cu+7H_2SO_4\rightarrow 3CuSO_4+Cr_2(SO_4)_3+K_2SO_4+7H_2O$

By Stoichiometry of the reaction:

3 moles of copper reacts with 1 mole of potassium dichromate.

So, 0.067 moles of copper will react with = $\frac{1}{3}\times 0.067=0.022mol$ of potassium dichromate

To calculate the volume of potassium dichromate, we use the equation:

$\text{Molarity of the solution}=\frac{\text{Moles of solute}}{\text{Volume of solution (in L)}}$

We are given:

Moles of potassium dichromate = 0.022 mol

Molarity of solution = 0.800 M

Putting values in above equation, we get:

$0.08mol/L=\frac{0.022mol}{\text{Volume of solution}}\\\\\text{Volume of solution}=0.0275L$

Hence, the volume of solution required is 0.0275 L.