Half life

Q. When initial concentration of the reactant is doubled, the half-life period of a zero order reaction:

1. Is tripled
2. Is doubled
3. Is halved
4. Remains unchanged

Q. Half life of a first-order reaction is $1386seconds$. The specific rate constant of the reaction is :

1. $5.0\times {10}^{-2}{s}^{-1}$
2. $5.0\times {10}^{-3}{s}^{-1}$
3. $0.5\times {10}^{-3}{s}^{-1}$
4. $0.5\times {10}^{-2}{s}^{-1}$

Q. $nA\to B$ is a $1^{st}$ order reaction, whose concentration versus time curve is given below

If the half - life for the reaction is 24 minutes, then the value of n is

1. 1
2. 2
3. 3
4. 4

Q. A first order reaction has a rate constant of ${10}^{-2}se{c}^{-1}$. How long will it take for a 20 g sample to become 5 g?

1. 138.6

Q. Match the following order of the reactions with their half-life periods

1. $(k{a}_0{)}^{-1}$
2. $\frac{0.693}{k}$
3. $\frac{a_0}{2k}$

Q. Concentrations of A, B and C vs time are graphed for the reaction $A⟶3B+C$. The rate of the reaction is defined as r = k [A] $(log2=0.3,log3=0.48)$
Find the correct options:

1. $t_2=5t_1$
2. $\left[A\right]$ at $t_2=1M$
3. $C_1=3M$
4. $t_{\frac{1}{2}}=20min$

Q. Which of the following relationship(s) is/are correct for a $1^{st}$ order reaction?

1. $t_{75\%}=2t_{1/2}$
2. $t_{87.5\%}=3t_{1/2}$
3. $t_{99.9\%}=9t_{1/2}$
4. $t_{96.87\%}=4t_{1/2}$

Q. Arun got a first order reaction to set up in a laboratory. He observed for 16 minutes and noticed that the reaction is $50\%$ complete. How much time will it take for the reaction to be $75\%$ complete?

1. 24 minutes
2. 32 minutes
3. 28 minutes
4. 48 minutes

Q.

What is the value of half-life of a first-order reaction?

Q. The half-life of a reaction is 50 minutes at a certain initial concentration. When the concentration is reduced to one-half, the half-life is found to be 25 minutes. The order of the reaction is:

1. Zero
2. One
3. Two
4. Three

Q. In a zero order reaction for every ${10}^{\circ }C$ rice of temperature, the rate is doubled. If the temperature is increased from ${10}^{\circ }C$ to ${100}^{\circ }C$, the rate of the reaction will become:

1. 256 times
2. 512 times
3. 64 times
4. 128 times

Q. Half life of a first-order reaction is $1386seconds$. The specific rate constant of the reaction is :

1. $5.0\times {10}^{-2}{s}^{-1}$
2. $5.0\times {10}^{-3}{s}^{-1}$
3. $0.5\times {10}^{-2}{s}^{-1}$
4. $0.5\times {10}^{-3}{s}^{-1}$

Q.

Under the same reaction conditions, the initial concentration of 1.386 mol $d{m}^{-3}$ of a substance becomes half in 40 seconds and 20 seconds 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. $0.5$
2. $1.0$
3. $1.5$
4. $2.0$

Q. For a first order reaction, the time taken for the initial concentration to become $1/4^{th}$, is 10 minutes. What will be the time required to reduce the initial concentration to 1/16 of the initial value?

1. 10 min
2. 20 min
3. 30 min
4. 40 min

Q. The graph between $\log T_{50}$ and $\log \left(\frac{1}{a}\right)$ (where $T_{50}$ and a are the half - life period and the concentration respectively) for a $n^{th}$ order reaction is of the type:

What is the value of n?

Q.

(A) follows first order reaction, (A) $\to$ product.

The concentration of A changes from 0.1 to 0.025 M in 40 min.

Find the rate of reaction of A when the concentration of A is 0.01 M.

1. $3.47\times {10}^{-4}Mmi{n}^{-1}$

2. $1.73\times {10}^{-4}Mmi{n}^{-1}$

3. $1.73\times {10}^{-5}Mmi{n}^{-1}$

4. $3.47\times {10}^{-5}Mmi{n}^{-1}$

Q.

The half-life period of a first order chemical reaction is 6.93 minutes.
The time required for 99% completion of reaction will be (log 2 = 0.301)

1. 230.3 min

2. 23.03 min

3. 46.06 min

4. 460.6 min

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

Q.

The half - time period of a radioactive element is 140 days. After 650 days, one gram of the element will reduce to (J 1986)

1. $\frac{1}{2}g$

2. $\frac{1}{4}g$

3. $\frac{1}{8}g$

4. $\frac{1}{16}g$

Q. The rate of a first order reaction is $0.69\times {10}^{-2}mi{n}^{-1}$and the initial concentration is 0.5 mol/L. The half life period is

1. 3000 s
2. 0.33 s
3. 50 s
4. 100 s

Q. The rate of a first order reaction is $0.69\times {10}^{-2}mi{n}^{-1}$and the initial concentration is 0.5 mol/L. The half life period is

1. 3000 s
2. 0.33 s
3. 50 s
4. 100 s

Q. For a reaction represented by $A\to B$, which of the following options give the value of order of the reaction.
$ROR=$ Rate of reaction
$C=$ Concentration of reactant $A$
$C_0=$ Concentration of reactant $A$ at $t=0$
$P=$ Concentration of product $B$
$t_{\frac{1}{2}}=$ Half life of $A$

1. $\frac{\log (ROR{)}_2-\log (ROR{)}_1}{\log C_2-\log C_1}$
2. $1+\left[\frac{\log t_{1/2}^{\prime }-\log t_{1/2}}{\log C_0-\log C_0^{\prime }}\right]$
3. Slope of $\ln ROR$ vs $\ln C$ graph
4. "$y-$ intercept" of $\ln ROR$ vs $\ln C$ graph

Q. For a certain reaction of order ‘n’, the half-life $\left(t_{\frac{1}{2}}\right)$ is given by, $t_{\frac{1}{2}}=\frac{2-\sqrt{2}}{k}\times C_0^{\frac{1}{2}}$, where k is a constant and $C_0$ is the initial concentration. Find 'n'.

Q.

In a first order reaction, the concentration of the reactant decreases from 800 mol $d{m}^{-3}$ to 50 mol $d{m}^{-3}$ in $2\times {10}^{4}s.$ The rate constant of the reaction in $\left(s^{-1}\right)$ is
(IIT-JEE, 2003)

1. $2\times {10}^4$
2. $3.45\times {10}^{-5}$
3. $1.386\times {10}^{-4}$
4. $2\times {10}^{-4}$

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.

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. 1

4. 0.5

Q. Concentrations of A, B and C vs time are graphed for the reaction $A⟶3B+C$. The rate of the reaction is defined as r = k [A] $(log2=0.3,log3=0.48)$
Find the correct options:

1. $t_2=5t_1$
2. $\left[A\right]$ at $t_2=1M$
3. $C_1=3M$
4. $t_{\frac{1}{2}}=20min$

Q. In a zero order reaction for every ${10}^{\circ }C$ rice of temperature, the rate is doubled. If the temperature is increased from ${10}^{\circ }C$ to ${100}^{\circ }C$, the rate of the reaction will become:

1. 256 times
2. 512 times
3. 64 times
4. 128 times

Q.

1. Zero
2. One
3. Two
4. Three

Q. Concentrations of A, B and C vs time are graphed for the reaction $A⟶3B+C$. The rate of the reaction is defined as r = k [A] $(log2=0.3,log3=0.48)$
Find the correct options:

1. $t_2=5t_1$
2. $\left[A\right]$ at $t_2=1M$
3. $C_1=3M$
4. $t_{\frac{1}{2}}=20min$