Question

One way in which the useful metal copper is produced is by dissolving the mineral azurite, which contains copper(II) carbonate, in concentrated sulfuric acid. The sulfuric acid reacts with the copper(II) carbonate to produce a blue solution of copper(II) sulfate. Scrap iron is then added to this solution, and pure copper metal precipitates out because of the following chemical reaction:

Fe

(s)

+

CuSO4

(aq)

→

Cu

(s)

+

FeSO4

(aq)

Suppose an industrial quality-control chemist analyzes a sample from a copper processing plant in the following way. He adds powdered iron to a

500.mL

copper(II) sulfate sample from the plant until no more copper will precipitate. He then washes, dries, and weighs the precipitate, and finds that it has a mass of

65.mg

.

Calculate the original concentration of copper(II) sulfate in the sample. Round your answer to

2

significant digits.

Answer 1

original concentration of copper(II) sulfate = 2.0 x 10^-3 M

Explanation

mass Cu = 65 mg = 65 x 10^-3 g

moles Cu = (mass Cu) / (molar mass Cu)

moles Cu = (65 x 10^-3 g) / (63.546 g/mol)

moles Cu = 1.023 x 10^-3 mol

moles CuSO₄ present = moles Cu

moles CuSO₄ present = 1.023 x 10^-3 mol

original concentration of CuSO₄ = (moles CuSO₄ present) / (volume of sample)

original concentration of CuSO₄ = = (1.023 x 10^-3 mol) / (500. x 10^-3 L)

original concentration of CuSO₄ = 2.0 x 10^-3 M