A first order reaction is 20% complete in 10 min. The specific rate constant is:

• (A) 0.0223 min^-1
• (B) 0.0423 min^-1
• (C) 0.0501 min^-1
• (D) 0.0517 min^-1

To find the specific rate constant for a first-order reaction that is 20% complete in 10 minutes, we can use the first-order reaction formula:

First-Order Reaction Formula

The equation is:

ln([A]₀/[A]) = kt

Where:

• [A]₀ = initial concentration
• [A] = concentration at time t
• k = rate constant
• t = time

Calculating Concentrations

If the reaction is 20% complete, then 80% of the reactant remains. This means:

[A] = 0.80[A]₀

Substituting Values

Plugging this into the equation gives:

ln([A]₀/(0.80[A]₀)) = kt

This simplifies to:

ln(1.25) = kt

Finding k

Now, we know:

• ln(1.25) ≈ 0.2231
• t = 10 min

Thus, we can rearrange the equation to solve for k:

k = ln(1.25) / t = 0.2231 / 10

k ≈ 0.02231 min^-1

Final Answer

The specific rate constant is approximately 0.0223 min^-1, which corresponds to option (A).