Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
JEE Advanced 2006
Exam
JEE Advanced
Year
2006
Subject
Chemistry
Chapter
Chemical Kinetics

JEE Advanced 2006 · Chemistry · Chemical Kinetics

Paragraph: Carbon-14 is used to determine the age of organic...

Paragraph: Carbon-14 is used to determine the age of organic material. The procedure is based on the formation of 14C{ }^{14} \mathrm{C} by neutron capture in the upper atmosphere. { }_7^{14} \mathrm{~N}+{ }_0^1 n \longrightarrow{ }_6^{14} \mathrm{C}+{ }_1 n¹ 14C{ }^{14} \mathrm{C} is absorbed by living organisms during photosynthesis. The 14C{ }^{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 14C{ }^{14} \mathrm{C} in the dead being, falls to the decay which 14C{ }^{14} \mathrm{C} undergoes. { }_6^{14} \mathrm{C} \longrightarrow{ }_7^{14}  N+β−\mathrm{~N}+\beta^{-}The half life period of 14C{ }^{14} \mathrm{C} is 5770 years. The decay constant (λ)(\lambda) can be calculated by using the following formula λ=0.693t1/2\lambda=\frac{0.693}{t_{1/2}}. The comparison of the β−\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 14C{ }^{14} \mathrm{C} to 12C{ }^{12} \mathrm{C} in living matter is 1:10121: 10^{12}.Question: A nuclear explosion has taken place leading to increase in concentration of C14C^{14} in nearby areas. C14\mathrm{C}^{14} concentration is C1C_1 in nearby areas and C2C_2 in areas far away. If the age of the fossil is determined to be T1T_1 and T2T_2 at the places respectively then

Options

  1. AThe age of the fossil will increase at the place where explosion has taken and T1−T2=1λln⁡C1C2T_1-T_2=\frac{1}{\lambda} \ln \frac{C_1}{C_2}
  2. BThe age of the fossil will decrease at the place where explosion has taken place and T1−T2=1λln⁡C1C2T_1-T_2=\frac{1}{\lambda} \ln \frac{C_1}{C_2}
  3. CThe age of fossil will be determined to be same
  4. DT1T2=C1C2\frac{T_1}{T_2}=\frac{C_1}{C_2}

Correct answer

A. The age of the fossil will increase at the place where explosion has taken and T1−T2=1λln⁡C1C2T_1-T_2=\frac{1}{\lambda} \ln \frac{C_1}{C_2}

Step-by-step solution

All radioactive decays are the examples of first order kinetics. So, decay constant λ=1T1−T2ln⁡C1C2\lambda=\frac{1}{T_1-T_2} \ln \frac{C_1}{C_2} C1C_1 is the concentration at T1T_1 time C2C_2 is the concentration at T2T_2 time So, T1−T2=1λln⁡C1C2\quad T_1-T_2=\frac{1}{\lambda} \ln \frac{C_1}{C_2}
Practice Chemical Kinetics on Quantrex Academy →

More from Chemical Kinetics

For a reversible reaction R leftharpoons P , at constant temperature, both the forward… JEE Advanced 2026For a first-order reaction R P at a given temperature, k is the rate constant. For this… JEE Advanced 2026Given below are two statements: R=8.314 J K ^ -1 mol ^ -1 and 1 cal =4.2 J Statement I… JEE Main 2026Decomposition of a hydrocarbon follows the equation k = (5.5 × 10^ 11 \,s^ -1 )\,e^… JEE Main 2026For a reaction A arrow P at T K , the half life (t_ 1/2 ) is plotted as a function of… JEE Main 2026First order gas phase reaction A arrow B + C p_i = initial pressure of gas A, p_t = total… JEE Main 2026If the half life of a first order reaction is 6.93 minutes then the time required for… JEE Main 2026Consider the given graph showing variation of reactant concentration with time. Three… JEE Main 2026 Full Chemical Kinetics list All JEE Advanced PYQs