# Chemistry Class 12 NCERT Solutions: Chapter 4 Chemical-Kinetic Part 10 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Q: 20. For the decomposition of azoisopropane to hexane and nitrogen at , the following data are obtained.

t (sec) | P (mm of Hg) |

Calculate the rate constant.

After time, t, total pressure,

Therefore,

For a first order reaction,

When

When

Hence, the average value of rate constant is

Note:- There is a slight variation in this answer and the one given in the NCERT textbook.

Q: 21. The following data were obtained during the first order thermal decomposition of at a constant volume.

Experiment | Total pressure/atm | |

1 | 0 | 0.5 |

2 | 100 | 0.6 |

Calculate the rate of the reaction when total pressure is .

Answer:

The thermal decomposition of at a constant volume is represented by the following equation

After time, total pressure,

Therefore,

For a first order reaction,

When

When ,

Therefore, when the total pressure is , pressure of is

Therefore, the rate of equation, when total pressure is , is given by,