Half Life

Q.

Under the same reaction conditions, the initial concentration of 1.386 mol $d{m}^{-3}$ of a substance becomes half in 40 s and 20 s through first order and zero order kinetics, respectively.

The ratio $(k_1/k_0$ of the rate constants for first order $\left(k_1\right)$ and zero order $\left(k_0\right)$of the reaction is

1. $0.5mol{}^{-1}d{m}^3$
2. $1.0mold{m}^{-3}$
3. $1.5mold{m}^{-3}$
4. $2.0mol{}^{-1}d{m}^3$

Q. For a reaction A to B, the reaction is quadrupled when the concentration is doubled the rate expression of the reaction is r=k[A]^n where the value of n is
a)3
b)2
c)1
d)0

Q. The ratio of the time taken for 99.9$\%$ reaction and half life of the reaction is

1. 100
2. 49.95
3. 10
4. 1000

Q. The half-life of a first order reaction is 24 hrs. If we start with 10 M initial concentration of the reactant then conc. after 96 hrs will be

1. 6.25 M
2. 1.25 M
3. 0.125 M
4. 0.625 M

Q. Q. the ratio of de broglie wavelength of a deuterium atom to that of an particle , when the velocity of the former is five times greater than that of the later is (a) 4 (b)0.2 (c)2 (d)0.4 (e) 5

Q. Starting with one mole of a compound X, it is found that the reaction is $\frac{3}{4}$, complete in 1 min. What is the rate constant if the reaction follows first order?

1. $0.231s^{-1}$
2. $2.31s^{-1}$
3. $0.0231s^{-1}$
4. $2.31\times {10}^{-3}s-1$

Q.

Under the same reaction conditions, initial concentration of 1.386 $mold{m}^{-3}$ of a substance becomes half in 40 s amd 20 s through first order and zero order kinetics respectively. Ratio $\left(\frac{k_1}{k_0}\right)$ of the rate constants for first order $\left(k_1\right)$ and zero order $\left(k_0\right)$ of the reaction is:

1. $0.5mo{l}^{-1}d{m}^3$

2. $1.0mold{m}^{-3}$

3. $2.0mo{l}^{-1}d{m}^3$

4. $1.5mold{m}^{-3}$

Q. A first order reaction is half completed in 45 minutes. How long does it need for 99.9% of the reaction to be completed?

1. 20 hours
2. 10 hours
3. 7.5 hours
4. 5 hours

Q. If 8 g of a radioactive isotope has a half life period of 10 hrs, the half-life period of 2g of the same substance is

1. 2.5 hrs
2. 5 hrs
3. 10 hrs
4. 40 hrs

Q. If 7/8 of radioactive substance disintegrate in 12 days. Its half Ilfe period

Q. The half life of a first order reaction is

1. Independent of the initial concentration of the reactant
2. Directly proportional to the initial concentration of the reactant
3. Inversely proportional to the initial concentration of the reactant
4. Directly proportional to the square of the initial concentration of the reactant

Q.

What is a half-life?

Q. The half-life for the reaction, $N_2{O}_5\Rightarrow 2N{O}_2+\frac{1}{2}{O}_2$ is 12 minutes at ${30}^{\circ }C$. Starting with 100 g of $N_2{O}_5$ how many gram of $N_2{O}_5$ will remain after a period of 1 hour 36 minutes.

1. 1.25 g
2. 0.39 g
3. 1.77 g
4. 0.5 g

Q. If the rate of reaction A → B doubles on increasing the concentration of A by 4 times, the order of the reaction is

1. 2
2. 1
3. 1/2
4. None

Q. The half - life period of radioactive element depends upon:

1. the amount of the element
2. the pressure
3. the temperature
4. none of the above

Q.

How rate of reaction depends upon concentration

Q. a sample of nitrogen contains 90%N14 and 10 %N15 isotopes.the average number of neutrons per atom is

Q. A radioactive isotope is being produced at a constant rate dN/dt = R in an experiment. The isotope has a half-life t_1/2. Show that after a time t >> t_1/2 the number of active nuclei will become constant. Find the value of this constant.

Q.

the radioactive isotopes decay at such a rate that after 192 minute only 1/16 of original amount remain. calculate the half life period.