Question

For a reaction : \( N_2 + 3H_2 \rightarrow 2NH_3 \), the rate of reaction with respect to \( NH_3 \) is

• A. \( +\frac{1}{3} \frac{\Delta [NH_3]}{\Delta t} \)
• B. \( -\frac{1}{2} \frac{\Delta [NH_3]}{\Delta t} \)
• C. \( +\frac{1}{4} \frac{\Delta [NH_3]}{\Delta t} \)
• D. \( +\frac{1}{2} \frac{\Delta [NH_3]}{\Delta t} \)

Hint:

Always use negative signs for reactants (disappearance) and positive signs for products (appearance). The coefficient always goes in the denominator.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
The rate of a reaction can be expressed in terms of any of its reactants or products by dividing the rate of change of their concentration by their respective stoichiometric coefficients.
Step 2: Detailed Explanation:
Given reaction: \( 1N_2 + 3H_2 \rightarrow 2NH_3 \).
The stoichiometric coefficient of the product \( NH_3 \) is 2.
The rate of formation of \( NH_3 \) is \( \frac{\Delta [NH_3]}{\Delta t} \).
To find the overall rate of reaction with respect to \( NH_3 \), we use a positive sign (since it is a product) and divide by its coefficient:
\[ \text{Rate} = +\frac{1}{2} \frac{\Delta [NH_3]}{\Delta t} \]
Step 3: Final Answer:
The correct rate expression is \( +\frac{1}{2} \frac{\Delta [NH_3]}{\Delta t} \).