Answer the following questions about second-order reactions. What is the rate co
ID: 983356 • Letter: A
Question
Answer the following questions about second-order reactions. What is the rate constant for the reaction 2 A rightarrow B + 2 C, given that the concentration of A decreases from 2.50 mmol/L to 1.25 mmol/L in 100. s What is the rate constant for the reaction A rightarrow C + 2 D, given that [A]_0 = 0.300 M and that the concentration of C increases to 0.010 M in 200. s How much time is required for the concentration of B to increase to 0.19 M when [A]_0 = 0.15 M, given that k = 0.0035 M^-1 min^-1 in the rate law for the loss of A in the reaction A rightarrow 2 B + CExplanation / Answer
a)
[Ao] = 2.5 mmol/L = 2.5*10^-3 M
rate = 1/2*change in concentration of A / chnage in time
= 1/2(2.5-1.25) / 100
=0.5*0.0125 mmol/L/s
=6.25*10^-6 M/s
FOR 2ND ORDER,
USE:
rate = k[Ao]^2
6.25*10^-6 M/s= K* (2.5*10^-3 M)^2
k = 1 M-1s-1
Answer: 1 M-1s-1 or 1 L/mol-s
b)
[Ao] = 0.3 M
rate =change in concentration of C / chnage in time
= 0.01 / 200
=5*10^-5 M/s
FOR 2ND ORDER,
USE:
rate = k[Ao]^2
5*10^-5 M/s= K* (0.3 M)^2
k = 5.56*10^-4 M-1s-1
Answer: 5.56*10^-4 M-1s-1
C)
rate = k[Ao]^2
=0.0035 * (0.15)^2
=7.875*10^-5 M/min
for B:
rate = 1/2 * change in concentration of B / time
7.875*10^-5 = 1/2 *0.19/time
time = 1206 min
Answer: 1206 min