Question 1 of 37beginner🔧 ApplyNumerical2 marks

For the reaction R→PR \rightarrow P, the concentration of a reactant changes from 0.03M to 0.02M in 25 minutes. Calculate the average rate of reaction using units of time both in minutes and seconds.

Correct Answer

Average rate of reaction = 4×104 \times 10⁻⁴ mol L⁻¹ min⁻¹ (in minutes) Average rate of reaction = 6.67×106.67 \times 10⁻⁶ mol L⁻¹ s⁻¹ (in seconds)

Exercise: Intext Questions | Q: 3.1 | (Page 6)
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Explanation

This question tests understanding of average rate of reaction calculation. From the context, the rate of disappearance of reactant R is given by: Rate = -Δ[R]/Δt. Since Δ[R] is negative (concentration decreases), multiplying by -1 makes the rate positive. The change in concentration is 0.01 M (from 0.03M to 0.02M) over 25 minutes. Students must calculate rate in both minutes and seconds, showing proper units.

Solution Steps

  1. Step 1: Identify given values - Initial concentration [R]₁ = 0.03 M, Final concentration [R]₂ = 0.02 M, Time (Δt) = 25 minutes

  2. Step 2: Calculate change in concentration - Δ[R] = [R]₂ - [R]₁ = 0.02 - 0.03 = -0.01 M

  3. Step 3: Apply formula for average rate - Rate = -Δ[R]/Δt = -(-0.01)/25 = 0.01/25 = 4×104 \times 10⁻⁴ mol L⁻¹ min⁻¹

  4. Step 4: Convert time to seconds - 25 minutes = 25×6025 \times 60 = 1500 seconds

  5. Step 5: Calculate rate in seconds - Rate = 0.01/1500 = 6.67×106.67 \times 10⁻⁶ mol L⁻¹ s⁻¹

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