Question

Which of the following reactions is not correct with respect to products formed?

• A. \(3{Cu} + 8{HNO}_3 {(dilute)} \rightarrow 3{Cu(NO}_3)_2 + {N}_2{O} + 4{H}_2{O}\)
• B. \(4{Zn} + 10{HNO}_3 {(dilute)} \rightarrow 4{Zn(NO}_3)_2 + {N}_2{O} + 5{H}_2{O}\)
• C. \( {Cu} + 4{HNO}_3 {(conc)} \rightarrow {Cu(NO}_3)_2 + 2{NO}_2 + 2{H}_2{O}\)
• D. \( {Zn} + 4{HNO}_3 {(conc)} \rightarrow {Zn(NO}_3)_2 + 2{NO}_2 + 2{H}_2{O}\)

Hint:

It is essential to understand the typical products of reactions involving metals and nitric acid, as the concentration of the acid can significantly influence the nitrogen oxides formed.

Answer 1

The Correct Option is A

To solve this problem, we need to analyze the reactions involving copper (Cu), zinc (Zn), and their interactions with nitric acid (HNO₃) in both dilute and concentrated forms.

1. Understanding the Reaction Process:
In the reaction between metals and acids, especially nitric acid, the type of acid (dilute or concentrated) can significantly affect the products.

Copper (Cu) and zinc (Zn) react with nitric acid to form different products based on whether the acid is dilute or concentrated. For example, dilute nitric acid typically produces nitrogen oxides (like N₂O or NO), whereas concentrated nitric acid typically produces nitrogen dioxide (NO₂).

2. Analyzing Each Reaction:

Option 1: The reaction \( 3Cu + 8HNO_3 (\text{dilute}) \to 3Cu(NO_3)_2 + N_2O + 4H_2O \) is not correct. When copper reacts with dilute nitric acid, it typically forms Cu(NO₃)₂ and nitrogen oxides, but N₂O is not usually formed in this case, as copper generally forms Cu²⁺ ions in dilute nitric acid. This is the incorrect reaction.

Option 2: \( 4Zn + 10HNO_3 (\text{dilute}) \to 4Zn(NO_3)_2 + N_2O + 5H_2O \) is correct. Zinc reacts with dilute nitric acid to form zinc nitrate and nitrogen oxide (N₂O), as expected.

Option 3: \( Cu + 4HNO_3 (\text{conc}) \to Cu(NO_3)_2 + 2NO_2 + 2H_2O \) is correct. Copper reacts with concentrated nitric acid to form copper nitrate (Cu(NO₃)₂), nitrogen dioxide (NO₂), and water, which is a typical reaction.

Option 4: \( Zn + 4HNO_3 (\text{conc}) \to Zn(NO_3)_2 + 2NO_2 + 2H_2O \) is correct. Zinc reacts with concentrated nitric acid to form zinc nitrate (Zn(NO₃)₂), nitrogen dioxide (NO₂), and water, which is a typical reaction as well.

3. Conclusion:
The reaction in Option A is not correct because the product N₂O is not typically formed when copper reacts with dilute nitric acid. Therefore, Option 1 is the correct answer.

Final Answer:
The correct answer is Option A.