The decomposition of an aldehyde solution in carbon tetrachloride is a first order reaction with a rate constant of 1.20 x 10-3 min-l. If we start with [aldehyde] = 0.0500 molar, what will the concentration be 150 minutes later?

a. 0.00900 M b. 0.0418 M c. 0.00926 M d. 0.00499M e. 0.000333 M

First time on this site, really need some chemistry help with answer

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Use ln(No/N) = kt
You're given k, substitute that and the other values and solve for N.

According to our book we are supposed to use the following

ln (N/No) = -kt

Are both equations correct?

Yes. If you place a negative sign, then the ln No/N term is reversed (take the reciprocal).

To solve this problem, we can use the first-order reaction rate equation:

ln([A]/[A]0) = -kt

Where [A] is the concentration of the reactant at a given time, [A]0 is the initial concentration of the reactant, k is the rate constant, t is the time, and ln represents the natural logarithm.

We are given the rate constant, k = 1.20 x 10^(-3) min^(-1). The initial concentration, [A]0, is 0.0500 M. We need to find [A] at t = 150 minutes.

Plugging the values into the equation, we get:

ln([A]/0.0500) = -(1.20 x 10^(-3))(150)

Solving for [A], we have:

ln([A]/0.0500) = -0.18

Taking the antilog (e^(ln(x)) = x) of both sides, we get:

[A]/0.0500 = e^(-0.18)

[A] = (e^(-0.18))(0.0500)

Calculating this, we find:

[A] ≈ 0.00926 M

Therefore, the concentration of the aldehyde solution 150 minutes later is approximately 0.00926 M. So, the correct answer is option c: 0.00926 M.