Question

The reaction: 2A → C is first order. If the initial concentration of A is 1.0M and the rate constant is 7.7 x 10-3s-1 , What is the final concentration of A after 3.0 minutes?

A. 0.25

B. 0.72

C. 0.98

Answer 1

Answer on question #70359, Chemistry / Inorganic Chemistry

The reaction: $2\mathrm{A} \rightarrow \mathrm{C}$ is first order. If the initial concentration of A is 1.0M and the rate constant is $7.7 \times 10^{-3}\mathrm{s}^{-1}$, What is the final concentration of A after 3.0 minutes?

A. 0.25

B. 0.72

C. 0.98

**Solution:**

For the reaction of first order:

$$C _ {A} = C _ {0} \cdot e ^ {- k \cdot t}$$ $$C _ {0} = 1 M, \quad k = 7. 7 \cdot 1 0 ^ {- 3} s ^ {- 1}, \quad t = 3 m = 1 8 0 s.$$ $$C _ {A} = 1 \cdot e ^ {- 7. 7 \cdot 1 0 ^ {- 3} \cdot 1 8 0} = 0. 2 5 M.$$

**Answer:** A. 0.25.

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