Topic: Rate Equations
Question 1
Twi compounds, A and B , react in the following way:
A + 3B —> AB3.
using the data below, derive the rate equation for this reaction and explain your reasoning.(4 marks)
b) Use the experimental data provided below to determine the rate constant. ( 3 marks)
data:
Let the rate be given by r = k[A]x[B]y
1) 0.002 = k(0.100)x(0.100)y
2) 0.008 = k(0.100)x(0.200)y
3) 0.018 = k(0.100)x(0.300)y
4) 0.004 = k(0.200)x(0.100)y
5) 0.006 = k(0.300)x(0.100)y
From 1, 2 and 3
"\\dfrac{0.018}{0.008 } = \\dfrac{k(0.100)^x(0.300)^y}{k(0.100)^x(0.200)^y}"
"2.25 = (1.5)^y => y = 2"
OR
"\\dfrac{0.008}{0.002} = \\dfrac{k(0.100)^x(0.200)^y}{k(0.100)^x(0.100)^y}"
"4 = (2)^y => y = 2"
From 1, 4 and 5
"\\dfrac{0.004}{0.002} = \\dfrac{k(0.200)^x(0.100)^y}{k(0.100)^x(0.100)^y}"
"2 = (2)^x => x = 1"
OR
"\\dfrac{0.006}{0.002} = \\dfrac{k(0.300)^x(0.100)^y}{k(0.100)^x(0.100)^y}"
"3 = (3)^x => x = 1"
The rate equation for this reaction r = k[A][B]2
From experiment 1 the rate constant
"k=\\dfrac{0.002\\ mol\\ dm^{-3}\\ s^{-1}}{0.100\\ mol\\ dm^{-3}\\ *(0.100\\ mol\\ dm^{-3})^2}=2\\ dm^6\\ mol^{-2}\\ s^{-1}"
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