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.
2.
3.
4.
For a chemical reaction product, the postulated mechanism of the reaction is as follows.
\(E_{a_{1}} = 180 \ kJ \ mol^{-1}, \)
\( E_{a_{2}} = 90 \ kJ \ mol^{-1}, \)
\( E_{a_{3}} = 40 \ kJ \ mol^{-1}\)
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
For a first-order reaction , rate constant (k) [dependent on temperature (T)] was found
to follow the equation \(log \ k \ = \ (-2000)\frac{1}{T} \ + \ 6.0\). The pre-exponential factor A and
the activation energy , respectively, are:
1.
2.
3.
4.
An increase in the concentration of the reactants of a reaction leads to a change in:
1. | Heat of reaction | 2. | Threshold energy |
3. | Collision frequency | 4. | Activation energy |
The rate constant for a first-order reaction is . The time required to reduce 2.0 g of the reactant to 0.2 g will be:
1. | 200 s | 2. | 500 s |
3. | 1000 s | 4. | 100 s |
1. Pseudo-first-order reaction
2. First-order reaction
3. Second order reaction
4. Third-order reaction
For a general reaction A B, the plot of the concentration of A vs. time is given in the figure.
The slope of the curve will be:
1. | -k | 2. | -k/2 |
3. | -k2 | 4. | -k/3 |
The half-life of the two samples is 0.1 and 0.4 seconds, respectively. Their concentrations are 200 and 50, respectively. The order of the reactions will be:
1. 0
2. 2
3. 1
4. 4
For a reaction A → B, the Arrhenius equation is given as \(log_{e}k \ = \ 4 \ - \ \frac{1000}{T}\) the activation energy in J/mol for the given reaction will be:
1. 8314
2. 2000
3. 2814
4. 3412
A first-order reaction takes 40 min for 30 % decomposition. The half life of the reaction will be:
1. | 88.8 min | 2. | 94.3 min |
3. | 67.2 min | 4. | 77.7 min |