Science (English Medium) कक्षा १२ - CBSE Question Bank Solutions

Define the following modes of expressing the concentration of a solution. Which of these modes are independent of temperature and why?

V/V (volume percentage)

Define the following modes of expressing the concentration of a solution. Which of these modes are independent of temperature and why?

(iii) w/V (mass by volume percentage)

Define the following modes of expressing the concentration of a solution. Which of these modes are independent of temperature and why?

ppm. (parts per million)

Define the following modes of expressing the concentration of a solution. Which of these modes are independent of temperature and why?

x (mole fraction)

Define the following modes of expressing the concentration of a solution. Which of these modes are independent of temperature and why?

M (Molarity)

Define the following modes of expressing the concentration of a solution. Which of these modes are independent of temperature and why?

m (Molality)

Consider a first order gas phase decomposition reaction given below :
\[\ce{A(g) -> B(g) + C(g)}\]
The initial pressure of the system before decomposition of A was p_i. After lapse of time ‘t’, total pressure of the system increased by x units and became ‘p_t’ The rate constant k for the reaction is given as ______.

Which of the following statements is not correct about order of a reaction.

Rate law for the reaction \[\ce{A + 2B -> C}\] is found to be Rate = k [A][B]. Concentration of reactant ‘B’ is doubled, keeping the concentration of ‘A’ constant, the value of rate constant will be ______.

Compounds ‘A’ and ‘B’ react according to the following chemical equation.
\[\ce{A(g) + 2B(g) -> 2C(g)}\]
Concentration of either ‘A’ or ‘B’ were changed keeping the concentrations of one of the reactants constant and rates were measured as a function of initial concentration. Following results were obtained. Choose the correct option for the rate equations for this reaction.

The value of rate constant of a pseudo first order reaction ______.

Consider the reaction A ⇌ B. The concentration of both the reactants and the products varies exponentially with time. Which of the following figures correctly describes the change in concentration of reactants and products with time?

In any unimolecular reaction:

(i) only one reacting species is involved in the rate determining step.

(ii) the order and the molecularity of slowest step are equal to one.

(iii) the molecularity of the reaction is one and order is zero.

(iv) both molecularity and order of the reaction are one.

For a complex reaction:

(i) order of overall reaction is same as molecularity of the slowest step.

(ii) order of overall reaction is less than the molecularity of the slowest step.

(iii) order of overall reaction is greater than molecularity of the slowest step.

(iv) molecularity of the slowest step is never zero or non interger.

For which type of reactions, order and molecularity have the same value?

In a reaction if the concentration of reactant A is tripled, the rate of reaction becomes twenty seven times. What is the order of the reaction?

For a general reaction A → B, plot of concentration of A vs time is given in figure. Answer the following question on the basis of this graph.

(i) What is the order of the reaction?

(ii) What is the slope of the curve?

(iii) What are the units of rate constant?

Why is the probability of reaction with molecularity higher than three very rare?

Why does the rate of any reaction generally decreases during the course of the reaction?

Why can’t molecularity of any reaction be equal to zero?