Advertisements
Advertisements
Question
For the decomposition of azoisopropane to hexane and nitrogen at 543 K, the following data are obtained.
| t (sec) | P(mm of Hg) |
| 0 | 35.0 |
| 360 | 54.0 |
| 720 | 63.0 |
Calculate the rate constant.
Advertisements
Solution
Azoisopropane decomposes according to the following equation:
\[\ce{(CH3)2CHN = NCH(CH3)2_{(g)} -> N2_{(g)} + C6H14_{(g)}}\]
This action is of first order reaction.
Initial pressure P0 = 35.0 mm Hg
Decrease in pressure of azoisopropane after time t = P
Increase in N2 pressure = `P_(N_2)`
Increase in the pressure of hexane = `P_(C_6H_14)`
Total pressure of the mixture Pt = `P_A + P_(N_2) + P_(C_6H_14)`
Pt = (P0 – P) + P + P = P0 + P
P = Pt – P0
PA = P0 – (Pt – P0) = 2P0 – Pt
But PA ∝ a − x and P0 ∝ Pt
k = `2.303/t log P_0/(2P_0 - P_t)`
When t = 360 s,
k = `2.303/360 log 35/(2 xx 35 - 54)`
= `2.303/360 log 35/16`
= `2.303/360 log 2.1875`
= `2.303/360 xx 0.339`
k = 2.17 × 10–3 s–1
When, t = 720 s,
k = `2.303/720 log 35/(2 xx 35 - 63)`
= `2.303/720 log 35/7`
= `2.303/720 (log 35 - log 7)`
= `2.303/720 (1.544 - 0.845)`
= `2.303/720 xx 0.699`
k = 2.23 × 10–3 s–1
Rate constant = `((2.17 + 2.23))/2 xx 10^-3 s^-1`
= 2.20 × 10–3 s–1
RELATED QUESTIONS
Sucrose decomposes in acid solution into glucose and fructose according to the first order rate law with `t_(1/2)` = 3 hours. What fraction of the sample of sucrose remains after 8 hours?
Time required to decompose SO2Cl2 to half of its initial amount is 60 minutes. If the decomposition is a first order reaction, calculate the rate constant of the reaction.
In a pseudo first order hydrolysis of ester in water, the following results were obtained:
| t/s | 0 | 30 | 60 | 90 |
| [A]/mol L−1 | 0.55 | 0.31 | 0.17 | 0.085 |
Calculate the average rate of reaction between the time interval 30 to 60 seconds.
Following data are obtained for reaction :
N2O5 → 2NO2 + 1/2O2
| t/s | 0 | 300 | 600 |
| [N2O5]/mol L–1 | 1.6 × 10-2 | 0.8 × 10–2 | 0.4 × 10–2 |
1) Show that it follows first order reaction.
2) Calculate the half-life.
(Given log 2 = 0.3010, log 4 = 0.6021)
A first order reaction takes 20 minutes for 25% decomposition. Calculate the time when 75% of the reaction will be completed.
(Given : log = 2 = 0·3010, log 3 = 0·4771, log 4 = 0·6021)
Define order of reaction. How does order of a reaction differ from molecularity for a complex reaction?
A first order reaction is 50% complete in 25 minutes. Calculate the time for 80% completion of the reaction.
With the help of an example explain what is meant by pseudo first order reaction.
In the presence of acid, the initial concentration of cane sugar was reduced from 0.2 M to 0.1 Min 5 hours and to 0.05 Min 10 hours. The reaction must be of?
The rate constant of a first order reaction is 6.9 × 10–3s–1. How much time will it take to reduce the initial concentration to its 1/8th value?
First order reaction is 50% complete in 1.26 × 1014s. How much time could it take for 100% completion?
Time required to decompose SO2Cl2 to half of its initial concentration is 60 minutes. If the de-composite is a first order reaction, calculated the rate constant of the reaction-
Observe the graph shown in figure and answer the following questions:
- What is the order of the reaction?
- What is the slope of the curve?
- Write the relationship between k and t1/2 (half life period).
The decomposition of formic acid on gold surface follows first-order kinetics. If the rate constant at 300 K is 1.0 × 10−3 s−1 and the activation energy Ea = 11.488 kJ mol−1, the rate constant at 200 K is ______ × 10−5 s−1. (Round off to the Nearest Integer)
(Given R = 8.314 J mol−1 K−1)
A definite volume of H2O2 undergoing spontaneous decomposition required 22.8 c.c. of standard permanganate solution for titration. After 10 and 20 minutes respectively the volumes of permanganate required were 13.8 and 8.25 c.c. The time required for the decomposition to be half completed is ______ min.
The reaction \[\ce{SO2Cl2(g) -> SO2(g) + Cl2(g)}\] is a first-order gas reaction with k = 2.2 × 10−5 sec−1 at 320°C. The percentage of SO2Cl2 is decomposed on heating this gas for 90 min, is ______%.
What is the rate constant?
Define first-order reaction.
The following data were obtained during the decomposition of SO2Cl2 at the constant volume. SO2Cl2 →SO2(g) + Cl2(g)
| Time (s) | Total Pressure (bar) |
| 0 | 0.5 |
| 100 | 0.6 |
Calculate the rate constant of the reaction.
