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:

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

Answer 3

In option (C), AgNO3 reacts with the copper spoon because copper displaces silver from the silver nitrate solution. The reaction is:  \[ \text{Cu} + 2\text{AgNO}_3 \rightarrow \text{Cu(NO}_3)_2 + 2\text{Ag} \] In other options, no such reaction occurs due to the nature of the metals and solutions involved. Gold is unreactive with dilute HCl, zinc sulfate does not react with copper, and platinum is inert towards concentrated nitric acid.