Question

A. The half-life for a first order reaction in 49 minutes. What is the rate constant?B.For a second order reaction, the half-life is 726 seconds. Starting with a concentration of 0.600 M, how long will it take for the concentration to decrease to 0.150 M?C. The half-life for a first order reaction is 2768 years. Starting with a concentration of 0.345 M, what will the concentration be after 11,072 years?D. The half-life for first order reaction A is 75 minutes. The half-life for a different first order reaction B is 322 minutes. Which reaction has the faster rate? (A or B) Which reaction has the larger rate constant, k? (A or B)

Answer 1

Answer:

a) 0,014 min⁻¹

b) 1452 seconds.

c) 0,02156 M

d) The faster rate is for the reaction A. The largest rate constant, k, is for A reaction

Explanation:

a) For a first order reaction the half-life is:

$t_{1/2} = \frac{ln(2)}{k}$ (1) As half.life is 49 min. Rate constant -k- is: 0,014 min⁻¹

b) The half-life is defined as the time that takes in descompose the half of the initial concentration of a compound.

As half-life is 726s. In 726s the concentration will be 0,300M, In the next 726s the concentration will be 0,150M. Thus, thae time it takes to decrease concentration until 0,150M is 726s×2= 1452 seconds

c) In the same way, 11072 years are 4 half-life for this reaction, thus:

0,345M/2⁴ = 0,02156 M

d) By definition of half-life, the less half-life, the faster rate. Thus, The faster rate is for the reaction A.

By (1) half-life is inversely proportional to rate constant. Thus, the less half-life, the largest rate constant. The largest rate constant, k, is for A reaction

I hope it helps!