The rate constant for a certain reaction is = 8.00×10−3 . If the initial reactant concentration was 0.400 , what will the concentration be after 16.0 minutes?

You need units on the rate constant; otherwise we don't know the order.

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To find the concentration of the reactant after a certain time, we can use the first-order reaction equation:

[A] = [A₀] * e^(-kt)

Where:
[A] = Final concentration of reactant
[A₀] = Initial concentration of reactant
k = Rate constant of the reaction
t = Time elapsed

Given:
Rate constant, k = 8.00 × 10^(-3) min^(-1)
Initial concentration, [A₀] = 0.400 M
Time elapsed, t = 16.0 minutes

Plugging in the values into the equation, we get:

[A] = [A₀] * e^(-kt)
[A] = 0.400 * e^(-8.00 × 10^(-3) * 16.0)

To calculate this, we will need to use the exponential function in a scientific calculator or an online calculator. Let's solve it step by step:

1. Calculate the value inside the parentheses:
(-8.00 × 10^(-3)) * 16.0

2. Multiply the initial concentration by the result we obtained:
0.400 * e^(result)

3. Use a calculator to calculate the value of e raised to the power of the result.

4. Multiply the initial concentration by the calculated value from the previous step to find the final concentration.

Note: The math may seem complex, but by breaking it down step by step, you'll find the solution.