We heat the oxalic acid solution because without heat it is a slow process as much more energy than the activation power needed to react. Therefore to increase energy, the temperature should be...
Why can’t molecularity of any reaction be equal to zero?
Zero molecularity means that there is no reactant, therefore the reaction will not be possible. So if there is a reaction then its molecularity will be greater than the zero.
Why molecularity is applicable only for elementary reactions and order is applicable for elementary as well as complex reactions?
Molecularity works only in the elementary reaction as it is a single reaction and the rate depends on the concentration of each molecule. And in the case of complex reactions there are many...
Why can we not determine the order of a reaction by taking into consideration the balanced chemical equation?
Order of a reaction is involved in a reaction. In complex reactions, rate and order of the reaction depend on the slow reaction, so in such cases, the order does not depend entirely on the balanced...
Thermodynamic feasibility of the reaction alone cannot decide the rate of the reaction. Explain with the help of one example.
The thermodynamic feasibility of reaction alone cannot determine the rate of reaction because in order for a reaction to occur it is important that the molecules have a greater potential than the...
Why does the rate of any reaction generally decrease during the reaction?
The reaction rate decreases because the reactants will continue to be converted into products. The reaction rate always depends on the concentration of the reactants.
Why is the probability of reaction with molecularity higher than three very rare?
For a response to have more than three molecules, the correct position is not possible which makes this reaction unusual. Thus the probability of colliding more than three molecules at the same time...
Oxygen is available in plenty in the air yet fuels do not burn by themselves at room temperature. Explain.
Oxygen is found in the air but fuels do not burn themselves at room temperature because reactants must have a small amount of energy to form the products which is known as activation energy.
Why does the rate of a reaction increase with a rise in temperature?
The reaction rate increases with increasing temperature because at higher temperatures the friction of the colliding particles across the energy barrier will be larger. So the rate is also faster.
The reaction between H2(g) and O2(g) is highly feasible yet allowing the gases to stand at room temperature in the same vessel does not lead to the formation of water. Explain.
According to Maxwell Boltzmann's energy distribution curve, where the temperature T + 10 degree Celsius then the collision of molecular energy efficiency increases which leads to product formation....
For a general reaction A → B, plot of concentration of A vs time is given in Figure. Answer the following question based on this graph.
(i) What is the order of the reaction? (ii) What is the slope of the curve? (iii) What are the units of the rate constant? Answers: (i) Zero-order reaction is the order of reaction. (ii)...
For a zero-order reaction will the molecularity be equal to zero? Explain.
The molecularity of any reaction is the number of reactions involved in the basic reaction. Zero molecularity means that there is no reactant so reaction does not occur. Thus molecularity cannot be...
For a certain reaction large fraction of molecules has energy more than the threshold energy, yet the rate of reaction is very slow. Why?
The two most important responses that occur according to the collision theory are that the energy is greater than the activation energy and the correct position of the reactant molecules during a...
For a reaction A + B → Products, the rate law is — Rate = k [A][B]3/2 Can the reaction be an elementary reaction? Explain.
In an elementary reaction both the molecularity and order must be same. So, the given reaction is not an elementary reaction as the order of the given reaction is different.
Derive an expression to calculate the time required for completion of the zero-order reaction.
Let us take a reaction, R → P t=0 R = Reactant P = Product Rate = k[R]0 t=t –dR/dt = k , dR =-kdt Integrate on both the sides, ʃDr = -k ʃdt [R] = -kt + I If, t = 0 [R]= [R0] Then, I= R0 [R] = [R0]–...
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?
Let us take the rate of a reaction, Rate = k[A]α Multiplying the rate into twenty seven, 27 ˟ Rate = k[A]α Dividing the equations, α = 3 Hence, Order of the reaction = 3
For which type of reactions, order and molecularity have the same value?
The type of reaction that have the same value of order and molecularity is the elementary reaction. This type of reaction happens in only one step.
How can you determine the rate law of the following reaction? 2NO (g) + O2 (g) → 2NO2 (g)
Rate law of a reaction can be determined by the formula, Rate = k[NO]2[O2]1 The rate law can be measured by the reaction rate as the initial concentration activity by keeping the concentration of...
Write the rate equation for the reaction 2A + B → C if the order of the reaction is zero.
Rate Equation of the reaction: k[A]0[B]0 The concentration capacity of the reactants will be equal to zero. In the zero-order reaction, the rate constant and rate of the reaction is the same....
State a condition under which a bimolecular reaction is a kinetically first-order reaction.
Condition: A situation in which the order of a chemical reaction can be converted under it by taking a solvent or reactant at an exorbitant rate because its concentration does not change much. Let...
In any unimolecular reaction ______________.
(i) only one reacting species is involved in the rate-determining step. (ii) the order and the molecularity of the slowest step are equal to one. (iii) the molecularity of the reaction is one and...
For a complex reaction ______________.
(i) order of an overall reaction is the same as molecularity of the slowest step. (ii) order of an overall reaction is less than the molecularity of the slowest step. (iii) order of an overall...
At high pressure, the following reaction is zero order. 2NH3(g) →1130 K Platinum catalyst N2(g) + 3H2(g)
Which of the following options are correct for this reaction? (i) Rate of reaction = Rate constant (ii) Rate of the reaction depends on the concentration of ammonia. (iii) Rate of decomposition of...
During decomposition of an activated complex.
(i) energy is always released (ii) energy is always absorbed (iii) energy does not change (iv) reactants may be formed Correct Answers: (i) energy is always released (iv) reactants may be...
According to Maxwell Boltzmann distribution of energy, __________.
(i) the fraction of molecules with most probable kinetic energy decreases at higher temperatures. (ii) the fraction of molecules with most probable kinetic energy increases at higher temperatures....
In the graph showing Maxwell Boltzman distribution of energy, ___________.
(i) the area under the curve must not change with an increase in temperature. (ii) the area under the curve increases with increase in temperature. (iii) the area under the curve decreases with...
Which of the following statements are in accordance with the Arrhenius equation?
(i) Rate of a reaction increases with increase in temperature. (ii) Rate of a reaction increases with a decrease in activation energy. (iii) Rate constant decreases exponentially with an increase in...
Mark the incorrect statements.
(i) Catalyst provides an alternative pathway to a reaction mechanism. (ii) Catalyst raises the activation energy. (iii) A catalyst lowers the activation energy. (iv) Catalyst alters enthalpy change...
Which of the following graphs is correct for a zero-order reaction?
Correct Answers: Option (ii) Option (iv) Explanation: The graphs (ii) and (iv) represents a proper zero-order reaction.
Which of the following graphs is correct for a first-order reaction?
Correct Answers: Option (i) Option (iv) Explanation: The graphs (i) and (iv) represents a proper first-order reaction.
Compounds ‘A’ and ‘B’ react according to the following chemical equation. A (g) + 2 B (g) → 2C (g)
The concentration of either ‘A’ or ‘B’ was changed keeping the concentrations of one of the reactants constant and rates were measured as a function of initial concentration. Following results were...
Which of the following statement is not correct for the catalyst?
(i) It catalyses the forward and backward reaction to the same extent. (ii) It alters ∆G of the reaction. (iii) It is a substance that does not change the equilibrium constant of a reaction. (iv) It...
The value of rate constant of a pseudo first order reaction ____________.
(i) depends on the concentration of reactants present in a small amount. (ii) depends on the concentration of reactants present in excess. (iii) is independent of the concentration of reactants....
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?
Correct Answer: Option (ii) Explanation: The graph in the option (ii) describes the change in concentration of reactants and products with time.
Rate law cannot be determined from the balanced chemical equation if _______.
(i) the reverse reaction is involved. (ii) it is an elementary reaction. (iii) it is a sequence of elementary reactions. (iv) any of the reactants is in excess Correct Answers: (i) the...
Which of the following statements apply to a balanced chemical equation of an elementary reaction?
(i) Order is the same as molecularity. (ii) Order is less than the molecularity. (iii) Order is greater than the molecularity. (iv) Molecularity can never be zero. Correct Answers: (i) Order...
A first-order reaction is 50% completed in 1.26 × 1014 s. How much time would it take for 100% completion?
(i) 1.26 × 1015 s (ii) 2.52 × 1014 s (iii) 2.52 × 1028 s (iv) infinite Correct Answer: (iv) infinite Explanation: The time taken for the 100% completion of the reaction is...
Which of the following statements is incorrect about the collision theory of chemical reaction?
(i) It considers reacting molecules or atoms to be hard spheres and ignores their structural features. (ii) A number of effective collisions determine the rate of reaction. (iii) The collision of...
The rate law for the reaction A + 2B → C is found to be Rate = k [A][B]. The concentration of reactant ‘B’ is doubled, keeping the concentration of ‘A’ constant, the value of rate constant will be______.
(i) the same (ii) doubled (iii) quadrupled (iv) halved Correct Answer: (i) the same Explanation: For the given rate law of the reaction, if the concentration of reactant ‘B’ is doubled,...
Which of the following graph represents the exothermic reaction?
(i) (a) only (ii) (b) only (iii) (c) only (iv) (a) and (b) Correct Answer: (i) (a) only Explanation: The graph (a) represents the exothermic reaction.
Which of the following expressions is correct for the rate of reaction given below? 5Br–(aq) + BrO3–(aq) + 6H+(aq) → 3Br2(aq) + 3H2O(l)
Correct Answer: Option (iii) Explanation: The third option shows the correct expression for the rate of the reaction.
Which of the following statements is correct?
(i) The rate of a reaction decreases over time as the concentration of reactants decreases. (ii) The rate of a reaction is the same at any time during the reaction. (iii) The rate of a reaction is...
Consider the graph given in Figure. Which of the following options does not show the instantaneous rate of reaction at 40th second?
(i) V5-V2/50-30 (ii) V4-V2/50-30 (iii) V3-V2/40-30 (iv) V3-V1/40-20 Correct Answer: (i) V5-V2/50-30 Explanation: V5-V2/50-30 do not show instantaneous rate of reaction at 40th...
Which of the following statements is not correct about an order of a reaction.
(i) The order of a reaction can be a fractional number. (ii) Order of a reaction is experimentally determined quantity. (iii) The order of a reaction is always equal to the sum of the stoichiometric...
A graph of volume of hydrogen released vs time for the reaction between zinc and dil.HCl is given in Figure. On the basis of this mark the correct option.
(i) Average rate up to 40s is V3-V2/40 (ii) Average rate up to 40s is V3-V2/40-30 (iii) Average rate up to 40 seconds is V3/40 (iv) Average rate up to 40 seconds is V3-V1/40-20 Correct...
Consider the Arrhenius equation given below and mark the correct option. a–E /RT k = A e
(i) Rate constant increases exponentially with increasing activation energy and decreasing temperature. (ii) Rate constant decreases exponentially with increasing activation energy and decreasing...
According to Arrhenius equation rate constant k is equal to A e–E /RT a. Which of the following options represents the graph of ln k vs 1/T
Correct Answer: Option (i) Explanation: According to Arrhenius equation, the graph represented in the first option is a straight line with negative slope.
Consider a first order gas phase decomposition reaction given: A(g) → B(g) + C(g)
The initial pressure of the system before decomposition of A was pi. After lapse of time ‘t’, total pressure of the system increased by x units and became ‘pt The rate constant k for the reaction is...
Consider the Figure and mark the correct option.
(i) The activation energy of forwarding reaction is E1 + E2 and the product is less stable than reactant. (ii) The activation energy of forwarding reaction is E1+E2and product is more stable than...
Activation energy of a chemical reaction can be determined by _____________.
(i) determining the rate constant at standard temperature. (ii) determining the rate constants at two temperatures. (iii) determining the probability of collision. (iv) using catalyst. ...
In the presence of a catalyst, the heat evolved or absorbed during the reaction ___________.
(i) increases. (ii) decreases. (iii) remains unchanged. (iv) may increase or decrease. Correct Answer: (iii) remains unchanged Explanation: The enthalpy change of the reaction will not be...
The role of a catalyst is to change ______________.
(i) gibbs energy of reaction. (ii) enthalpy of reaction. (iii) activation energy of reaction. (iv) equilibrium constant. Correct Answer: (iii) activation energy of reaction Explanation: The...