Science (English Medium) Class 12 - CBSE Important Questions for Chemistry

For the reaction, \[\ce{A +2B → AB2}\], the order w.r.t. reactant A is 2 and w.r.t. reactant B. What will be change in rate of reaction if the concentration of A is doubled and B is halved?

Arrhenius equation can be represented graphically as follows:

The (i) intercept and (ii) slope of the graph are:

A first-order reaction takes 69.3 min for 50% completion. What is the time needed for 80% of the reaction to get completed? (Given: log 5 = 0.6990, log 8 = 0.9030, log 2 = 0.3010)

Explain how and why will the rate of reaction for a given reaction be affected when a catalyst is added.

Explain how and why will the rate of reaction for a given reaction be affected when the temperature at which the reaction was taking place is decreased.

The slope in the plot of ln[R] vs. time for a first order reaction is ______.

For the reaction 3A `rightarrow` 2B, rate of reaction `+ (d[B])/(dt)` is equal to ______.

The slope in the plot of [R] Vs. time for a zero-order reaction is ______.

The slope in the plot of `log  ["R"]_0/(["R"])` Vs. time for a first-order reaction is ______.

For the reaction \[\ce{3A -> 2B}\], rate of reaction `-("d"["A"])/"dt"` is equal to ______.

Assertion (A): For a zero-order reaction, the unit of rate constant and rate of reaction are same.

Reason (R): Rate of reaction for zero order reaction is independent of concentration of reactant.

Assertion (A): The half-life of a reaction is the time in which the concentration of the reactant is reduced to one-half of its initial concentration.

Reason (R): In first-order kinetics, when the concentration of reactant is doubled, its half-life is doubled.

Assertion (A): Order of reaction is applicable to elementary as well as complex reactions.

Reason (R): For a complex reaction, molecularity has no meaning.

Which of the following statement is true?

If the initial concentration of substance A is 1.5 M and after 120 seconds the concentration of substance A is 0.75 M, the rate constant for the reaction if it follows zero-order kinetics is ______.

Radioactive decay follows first-order kinetics. The initial amount of two radioactive elements X and Y is 1 gm each. What will be the ratio of X and Y after two days if their half-lives are 12 hours and 16 hours respectively?

A reaction is second order with respect to a reactant. How is the rate of reaction affected if the concentration of the reactant is reduced to half?

Which metal in the first transition series (3d series) exhibits + 1 oxidation state most frequently and why?

Which of the following cations are coloured in aqueous solutions and why ?

Sc³⁺, V³⁺, Ti⁴⁺, Mn²⁺ (At. Nos. Sc = 21, V = 23, Ti = 22, Mn = 25)

How would you account for the following? 

Transition metals exhibit variable oxidation states.