Half life

Q. The rate constant for a first order reaction whose half life is 480 sec is

1. $2.88\times {10}^{-2}{s}^{-1}$
2. $1.44\times {10}^{-3}{s}^{-1}$
3. $1.44s^{-1}$
4. $0.72\times {10}^{-3}{s}^{-1}$

Q.

16 g of radioactive radon is kept in a container. How much radon will disintegrate in 19 days? Half life of radon is 3.8 days.

1. 0.5 g

2. 5.5 g

3. 10.5 g

4. 15.5 g

Q. ${}_2^{M}A\left(g\right){\to }_{Z-4}^{M-8}B\left(g\right)+\alpha -particles$
The radioactive disintegration follows first order kinetics. Starting with 1 mol of in a 1 litre closed flask at ${27}^{\circ }$C, pressure set up after two half-lives is approximately

1. 40 atm
2. 25 atm
3. 12 atm
4. 37 atm

Q. The half life period of a radioactive element is $140$ days. After $560$ days the remaining amount of the element would be:

1. $1/2$ of the original amount
2. $1/8$ of the original amount
3. $1/16$ of the original amount
4. $1/4$ of the original amount

Q.

Half - lives of decomposition of $N{H}_3$ on the surface of a catalyst for different initial pressures are given as :
p(torr) 200 300 500
$t_{1.2\left(min\right)}$ 10 15 25
The order of the reaction is :

1. 2

2. 0

3. 0.5

4. 1