The time for half-life period of a certain reaction AProducts is 1 hour. When the initial concentration of the reactant 'A', is 2.0 mol L-1, how much time does it take for its concentration to come from 0.50 to 0.25 mol L-1 if it is a zero-order reaction?

1. 1 h

2. 4 h

3. 0.5 h

4. 0.25 h

Subtopic:  Order, Molecularity and Mechanism |
 63%
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The radionuclide T90234h undergoes two successive β-decays followed by one α-decay. the atomic number and the mass number respectively of the resulting radionucleide are:

(1) 92 and 234

(2) 94 and 230

(3) 90 and 230

(4) 92 and 230

Subtopic:  Order, Molecularity and Mechanism |
 69%
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A radioactive element has a half-life of 20 minute. How much time should elapse before the element is reduced to 1/8 its original value?

(1) 40 minute

(2) 60 minute

(3) 80 minute

(4) 160 minute

Subtopic:  First Order Reaction Kinetics |
 84%
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The half-life of 92U238 against \(\alpha\)-decay is 4.5 × 109 year The time taken in a year for the decay of the 15/16 part of this isotope will be:

1. 9.0×109

2. 1.8×1010

3. 4.5×109

4. 2.7×1010

Subtopic:  First Order Reaction Kinetics |
 79%
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A radioactive isotope has a half-life of 10 day. If today there are 125 g of it left, what was its original weight 40 day earlier?

(1) 600 g

(2) 1000 g

(3) 1250 g

(4) 2000 g

Subtopic:  First Order Reaction Kinetics |
 72%
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Two radioisotopes P and Q of atomic weight 10 and 20 respectively are mixed in equal amount by weight. After 20 days, their weight ratio is found to be 1:4. Isotope P has a half-life of 10 day. The half-life of isotope Q is:

(1) zero

(2) 5 day

(3) 20 day

(4) infinite

Subtopic:  First Order Reaction Kinetics |
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The rate constant of a reaction is 5.8 x 10-2 s-1. The order of the reaction is : 

1. First order

2. Zero order

3. Second order

4. Third order

Subtopic:  Order, Molecularity and Mechanism |
 88%
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For a chemical reaction A product, the postulated mechanism of the reaction is as follows.

Ak2k13BR.D.Sk3C
If the rate constants for individual reactions are  k1, k2 and k3, and activation energies are 
\(E_{a_{1}} = 180 \ kJ \ mol^{-1}, \)
\( E_{a_{2}} = 90 \ kJ \ mol^{-1}, \)
\( E_{a_{3}} = 40 \ kJ \ mol^{-1}\)
then overall activation energy for the reaction given above is

1. 70 kJ mol-1

2. -10 kJ mol-1

3. 310 kJ mol-1

4. 130 kJ mol-1

Subtopic:  Arrhenius Equation |
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The activation energy for a simple chemical reaction A  B is Ea in forward direction. The activation energy for reverse reaction :

(1) Can be less than or more than Ea

(2) Is always double of Ea

(3) Is negative of Ea

(4) Is always less than Ea

Subtopic:  Arrhenius Equation |
 74%
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3A  B + C

It would be a zero order reaction when :

(1) The rate of reaction is proportional to square of concentration of A

(2) The rate of reaction remains same at any concentration of A

(3) The rate remains unchanged at any concentration of B and C

(4) The rate of reaction doubles if concentration of B is increased to double.

Subtopic:  Definition, Rate Constant, Rate Law |
 76%
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