Chemical Kinetics

The rate constant of a reaction becomes four times when the temperature is increased. This indicates that:

1. The reaction order has increased.
2. The activation energy has become zero.
3. The reaction has become faster.
4. The concentration of reactants has increased automatically.

According to collision theory, a chemical reaction occurs only when the colliding molecules:

1. Possess any amount of kinetic energy.
2. Collide with low velocity.
3. Have sufficient energy and proper orientation.
4. Have equal masses.

The activation energy of a reaction is:

1. The total energy possessed by reactant molecules.
2. The minimum energy required for effective collisions.
3. The heat evolved during the reaction.
4. Equal to the enthalpy change of the reaction.

A catalyst increases the rate of a reaction by:

1. Increasing the activation energy.
2. Increasing the concentration of reactants.
3. Providing an alternative reaction pathway with lower activation energy.
4. Changing the equilibrium constant.

According to the Arrhenius equation, the rate constant of a reaction is given by:

1. k = A + Ea/RT
2. k = A e^(-Ea/RT)
3. k = Ea/RT
4. k = RT/Ea

The half-life of a first-order reaction is 20 minutes. The time required for the reactant concentration to decrease to one-fourth of its initial value is:

1. 10 minutes
2. 20 minutes
3. 30 minutes
4. 40 minutes

The integrated rate equation 1/[A] = 1/[A]0 + kt represents:

1. Zero-order reaction
2. First-order reaction
3. Second-order reaction
4. Third-order reaction

The rate constant of a reaction increases with temperature mainly because:

1. The concentration of reactants increases.
2. The activation energy decreases to zero.
3. A larger fraction of molecules possesses energy greater than the activation energy.
4. The reaction order changes.

Which graph gives a straight line for a first-order reaction?

1. Rate versus concentration
2. Concentration versus time
3. log[A] versus time
4. 1/[A] versus time

For a zero-order reaction, the concentration of the reactant decreases with time according to the equation:

1. [A] = [A]0 e^(-kt)
2. [A] = [A]0 - kt
3. log[A] = log[A]0 - (kt/2.303)
4. 1/[A] = 1/[A]0 + kt

For a first-order reaction, the half-life is given by:

1. t1/2 = 1/k
2. t1/2 = 0.693/k
3. t1/2 = 2.303/k
4. t1/2 = k/0.693

The unit of the rate constant for a first-order reaction is:

1. mol L^-1 s^-1
2. s^-1
3. L mol^-1 s^-1
4. mol^-2 L^2 s^-1

Which of the following statements about molecularity is correct?

1. It can be zero.
2. It may be fractional.
3. It is always a positive integer.
4. It is determined experimentally.

The rate law for a reaction is Rate = k[A]^2[B]. The overall order of the reaction is:

1. 1
2. 2
3. 3
4. 4

For the reaction 2A + B -> C, the rate of reaction is correctly expressed as:

1. Rate = -d[A]/dt
2. Rate = -(1/2) d[A]/dt = -d[B]/dt = d[C]/dt
3. Rate = d[A]/dt
4. Rate = d[B]/2dt