Question

In which of the following cases a chemical reaction is possible ?

• A. $ZnSO_{4(aq)}$ is placed in a copper vessel
• B. $AgNO_3$ solution is stirred with a copper spoon
• C. Conc. $HNO_3$ is stored in a platinum vessel
• D. gold ornaments are washed with dil $HCl$

Answer 1

The Correct Option is B

Let's evaluate each option for the possibility of a chemical reaction:
1. Gold ornaments are washed with dil. HCl: - Gold (Au) is a noble metal and does not react with dilute hydrochloric acid (HCl). Therefore, no chemical reaction will occur in this case.
2. ZnSO\(_4\) (aq) is placed in a copper vessel:
Zinc sulfate (ZnSO\(_4\)) is an aqueous solution, and copper is less reactive than zinc. When zinc sulfate solution is placed in a copper vessel, no reaction occurs between zinc sulfate and the copper vessel. However, if the copper vessel was placed in a more reactive metal, such as zinc, a reaction could occur. But in this case, the metal zinc is reacting with the copper solution.
3. AgNO\(_3\) solution is stirred with a copper spoon:
Copper (Cu) is more reactive than silver (Ag), so when AgNO\(_3\) solution is stirred with a copper spoon, copper will displace silver from silver nitrate, forming copper nitrate and silver. The reaction is: \[ \text{Cu} + 2\text{AgNO}_3 \rightarrow \text{Cu(NO}_3)_2 + 2\text{Ag}. \] Therefore, a chemical reaction is possible.
4. Conc. HNO\(_3\) is stored in a platinum vessel:
Platinum is an inert metal and does not react with concentrated nitric acid (HNO\(_3\)). Therefore, no reaction occurs in this case.

Thus, the correct answer is (B) ZnSO\(_4\) (aq) is placed in a copper vessel, as it is the only option where a chemical reaction is possible.

Answer 2

Platinum and gold lie at the bottom of the reactivity series. Thus it does not react with $HNO _{3}$ and $HCl$. Again, $Zn$ is more reactive than copper. Thus, copper will be displaced by $Zn$, if $ZnSO _{4}$ is placed in a copper vessel. But $Ag ^{+}$ is less reactive than copper. Thus, copper will displace silver. The corresponding reaction is:

$2 AgNO _{3}+ Cu \rightarrow Cu \left( NO _{3}\right)_{2}+2 Ag$