1
IIT-JEE 2008 Paper 1 Offline
MCQ (Single Correct Answer)
+3
-1

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

A
0.5 mol$$^{-1}$$ dm$$^3$$
B
1.0 mol dm$$^{-3}$$
C
1.5 mol dm$$^{-3}$$
D
2.0 mol$$^{-1}$$ dm$$^3$$
2
IIT-JEE 2007 Paper 2 Offline
MCQ (Single Correct Answer)
+3
-1
Consider a reaction aG + bH $$\to$$ Products. When concentration of both the reactants G and H is doubled, the rate increases by eight times. However, when concentration of G is doubled keeping the concentration of H fixed, the rate is doubled. The overall order of the reaction is
A
0
B
1
C
2
D
3
3
IIT-JEE 2006
MCQ (Single Correct Answer)
+3
-1

Carbon-14 is used to determine the age of organic material. The procedure is based on the formation of ${ }^{14} \mathrm{C}$ by neutron capture in the upper atmosphere.

$$ { }^{14} \mathrm{~N}+{ }_0^1 n \rightarrow{ }_6{ }^{14} \mathrm{C}+{ }_1^1 \mathrm{H} $$

${ }^{14} \mathrm{C}$ is absorbed by living organisms during photosynthesis. The ${ }^{14} \mathrm{C}$ content is constant in living organism once the plant or animal dies, the uptake of carbon dioxide by it ceases and the level of ${ }^{14} \mathrm{C}$ in the dead being, falls due to decay which ${ }^{14} \mathrm{C}$ undergoes.

$$ { }_6^{14} \mathrm{C} \rightarrow{ }_7^{14} \mathrm{~N}+\beta^{-} $$

The half-life period of ${ }^{14} \mathrm{C}$ is 5770 years. The decay constant ( $\lambda$ ) be calculated by using the following formula $\lambda=\frac{0.693}{t_{1 / 2}}$.

The comparison of the $\beta^{-}$activity of the dead matter with that of the carbon still in circulation enables measurement of the period of the isolation of the material from the living cycle. The method however, ceases to be accurate over periods longer than 30,000 years. The proportion of ${ }^{14} \mathrm{C}$ to ${ }^{12} \mathrm{C}$ in living matter is $1: 10^{12}$.

Which of the following option is correct?

A

In living organisms, circulation of ${ }^{14} \mathrm{C}$ from atmosphere is high, so the carbon content is constant in organism.

B

Carbon dating can be used to find out the age of earth crust and rocks.

C

Radioactive absorption due to cosmic radiation is equal to the rate of radioactive decay; hence, the carbon content remains constant in living organism.

D

Carbon dating cannot be used to determine concentration of ${ }^{14} \mathrm{C}$ in dead beings.

4
IIT-JEE 2006
MCQ (Single Correct Answer)
+3
-1

Carbon-14 is used to determine the age of organic material. The procedure is based on the formation of ${ }^{14} \mathrm{C}$ by neutron capture in the upper atmosphere.

$$ { }^{14} \mathrm{~N}+{ }_0^1 n \rightarrow{ }_6{ }^{14} \mathrm{C}+{ }_1^1 \mathrm{H} $$

${ }^{14} \mathrm{C}$ is absorbed by living organisms during photosynthesis. The ${ }^{14} \mathrm{C}$ content is constant in living organism once the plant or animal dies, the uptake of carbon dioxide by it ceases and the level of ${ }^{14} \mathrm{C}$ in the dead being, falls due to decay which ${ }^{14} \mathrm{C}$ undergoes.

$$ { }_6^{14} \mathrm{C} \rightarrow{ }_7^{14} \mathrm{~N}+\beta^{-} $$

The half-life period of ${ }^{14} \mathrm{C}$ is 5770 years. The decay constant ( $\lambda$ ) be calculated by using the following formula $\lambda=\frac{0.693}{t_{1 / 2}}$.

The comparison of the $\beta^{-}$activity of the dead matter with that of the carbon still in circulation enables measurement of the period of the isolation of the material from the living cycle. The method however, ceases to be accurate over periods longer than 30,000 years. The proportion of ${ }^{14} \mathrm{C}$ to ${ }^{12} \mathrm{C}$ in living matter is $1: 10^{12}$.

What should be the age of fossil for meaningful determination of its age?

A

6 years

B

6000 years

C

60,000 years

D

It can be used to calculate any age

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