Half-life pf a radioactive element is : from Chemistry Chemical

Previous Year Papers

Download Solved Question Papers Free for Offline Practice and view Solutions Online.

Test Series

Take Zigya Full and Sectional Test Series. Time it out for real assessment and get your results instantly.

Test Yourself

Practice and master your preparation for a specific topic or chapter. Check you scores at the end of the test.
Advertisement

 Multiple Choice QuestionsMultiple Choice Questions

681.

Which of the following reactions end infinite time ?

  • Zero order

  • 1st order

  • 2nd order

  • 3rd order


682.

Decay constant of a radioactive substance is 69.3 sec-1, find t116 of the same substance.

  • 4 × 10-2 sec

  • 2 × 10-2 sec

  • 1 × 10-2 sec

  • None of these


683.

A + 2B  C + D , if

d[A]dt = 5 x 10-4 mol L-1 s-1 , then - d[B]dt is

  • 2.5 x 10-4 mol L-1 s-1

  • 50 x 10-4 mol L-1 s-1

  • 2.5 x 10-3 mol L -1 s-1

  • 1.0 x 10-3 mol L -1 s-1


684.

Half-life of radioactive substance is 4 days . Amount of the substance decayed in two days is :

  • 12

  • 1 - 12

  • 20 %

  • 18


Advertisement
Advertisement

685.

Half-life pf a radioactive element is :

  • 0.693

  • 10.693

  • 0.693k

  • k0.693


C.

0.693k

For 1st order reactions (like radioactive decay) _ t1/20.693k


Advertisement
686.

Assertion : The kinetics of the reaction

mA + nB + pC → m'X + n'Y + p'Z

obeys the reaction as- dxdt = k[A]m[B]n

Reason : The rate of reaction does not depend upon the concentration of C.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both assertion and reason are true but reason is not the correct explanation of assertion.

  • If assertion is true but reason is false.

  • If both assertion and reason are false.


687.

For the reaction, 2N2O5  4NO2+ Orate of reaction is

  • 12ddt[N2O5]

  • 2ddt[N2O5]

  • 14ddt[NO2]

  • 4ddt[NO2]


688.

For reaction aA → xP, when [A] = 2.2 mM, the rate was found to be 2.4 mM s-1. On reducing concentration of A to half, the rate changes to 0.6 mM s-1. The order of reaction with respect to A is

  • 1.5

  • 2.0

  • 2.5

  • 3.0


Advertisement
689.

Assertion : According to transition state theory, for the formation of an activated complex, one of the vibrational degrees of freedom is converted into a translational degree of freedom.

Reason: Energy of the activated complex is higher than the energy of reactant molecules.

  • If both assertion and reason are true and reason is the correct explanation of the assertion.

  • If both assertion and reason are true but reason is not the correct explanation of the assertion.

  • If assertion is true, but reason is false.

  • Both assertion and reason are false statements.


690.

Which equation is correct for first order reactions ?

  • t1/2  C-1

  • t1/2  C

  • t1/2  Co

  • t1/2  C1/2


Advertisement