Chapter U1.6, Problem 6E

Interpretation Introduction

Interpretation:

The steps that may be dangerous in the lab while performing copper cycle reaction needs to be explained.

Concept introduction:

Copper cycle is based on the law of conservation of mass. During this cycle, the initial mass of the copper taken before the reaction is same as the amount obtained after the completion of all reactions. Thus, the mass of copper is conserved.

Explanation of Solution

There is following steps below which describe the reactions of copper cycle.

Step-1 : In first step, copper metal oxidized by nitric acid to form copper (II) nitrate ${\text{Cu(NO}}_3{)}_2$

Cu(s) + ${\text{HNO}}_3$ (aq)$\to$${\text{Cu(NO}}_3{)}_2$ (aq) + ${\text{NO}}_2\left(g\right)+H_{2}O\left(aq\right)$

Step-2: In second step, copper nitrate reacts with base (NaOH ) to form copper (II) hydroxide, ${\text{Cu(OH)}}_2$.

${\text{Cu(NO}}_3{\text{)}}_2(aq)+NaOH$ $ \to $$ Cu{(OH)}_2(s)+NaN{O}_3(aq)$$$

Step-3: In third step, copper (II) hydroxide is heated and it is transformed into copper (II) oxide.

$Cu{(OH)}_2(s)\to CuO(s)+H_{2}O(l)$

Step-4: In step fourth, copper (II) oxide reacts with acid, $H_{2}S{O}_4$ to form copper(II) sulfate,

$H_{2}S{O}_4(s)$ ).

$CuO(s)+H_{2}S{O}_4(s)$$\to$ $CuS{O}_4(aq)+H_{2}O(l)$

Step-5: Finally, copper ion in copper (II) sulfate is reduced to copper metal by magnesium.

$CuS{O}_4(aq)$ + Mg(s) $\to$Cu (s) + $MgS{O}_4(aq)$

One should wear safety goggles while performing the reactions. Chemicals like strong acid and base like H₂SO₄ and NaOH respectively are very dangerous if come in contact with human skin, clothing etc. In the first step, Cu reacts with nitric acid to produce brown gas $N{O}_2$ which is toxic. During centrifugation process, one should ensure to place tubes with the same volume of liquid with respect to each other.