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: Conceptual Overview:
The rate of a chemical reaction can be expressed in terms of the concentration change of any of its reactants or products, divided by their respective stoichiometric coefficients. This helps to standardize the rate expression for consistency in calculations.
Step 2: Detailed Analysis:
Consider the 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 represented as \( \frac{\Delta [NH_3]}{\Delta t} \).
To determine the overall rate of the 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: Conclusion:
The correct rate expression is \( +\frac{1}{2} \frac{\Delta [NH_3]}{\Delta t} \), indicating the rate of the reaction with respect to the formation of ammonia.