The reactions having very high values of energy of activation are generally________.
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M.C.Q (1 Marks)
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Chemical Kinetics questions
One sample from each question group in this chapter. Select any group above to see the full set with answer keys.
View full solution →
Which of the following is not correct reason for the substantially lower rate of reaction than the collision frequency?
In general, the rate of a reaction can be increased by all the factors except:
If hydrogen and oxygen are mixed and kept in the same vessel at room temperature, the reaction does not take place to form water because:
For a hypothetical reaction$: A + B \rightarrow$ Products, the rate law is $r = k[A][B]^0.$ The order of reaction is$:$
View full solution →In a reaction, $2A \rightarrow$ Products, the concentration of A decreases from $0.5 \ \ce{mol L^{–1}}$ to $0.4 \ \ce{mol L^{–1}}$ in $10$ minutes. Calculate the rate during this interval?
View full solution →For a reaction, $A + B \rightarrow$ Product; the rate law is given by, $r = k [ A]^{1/2} [B]^2.$ What is the order of the reaction?
View full solution →For the reaction $R \rightarrow P$, the concentration of a reactant changes from $0.03M$ to $0.02M$ in $25$ minutes. Calculate the average rate of reaction using units of time both in minutes and seconds.
View full solution →Define 'order of a reaction'.
Write the rate equation for the reaction $2\text{A + B}\xrightarrow{\ \ \ \ \ \ }\text{C}$ if the order of the reaction is zero.
View full solution →A certain reaction is $50\%$ complete in $20$ minutes at $300 K$ and the same reaction is again $50\%$ complete in $5$ minutes at $350 K.$ Calculate the activation energy if it is a first order reaction. $\ce{[R = 8.314 JK^{-1}mol^{-1}, \log 4 = 0.602]}.$
View full solution →How is the concept of coupling reactions useful in explaining the occurrence of non spontaneous thermochemical reactions? Explain giving an example.
For the first order thermal decomposition reaction, the following data were obtained:
$\text{C}_{2}\text{H}_{5}\text{Cl}\text{(g)}\rightarrow \text{C}_{2}\text{H}_{4}\text{(g)} + \text{HCl}\text{(g)} $
Calculate the rate constant
(Given: $\log 2 = 0.301, \log 3=0.4771, \log 4 =0.6021)$
View full solution →$\text{C}_{2}\text{H}_{5}\text{Cl}\text{(g)}\rightarrow \text{C}_{2}\text{H}_{4}\text{(g)} + \text{HCl}\text{(g)} $
| Time/sec | Total pressure/atm |
| $0$ | $0.30$ |
| $300$ | $0.50$ |
(Given: $\log 2 = 0.301, \log 3=0.4771, \log 4 =0.6021)$
A first order reaction takes 20 minutes for 25% decomposition. Calculate the time when 75% of the reaction will be completed. (Given : log 2 = 0·3010, log 3 = 0·4771, log 4 = 0·6021)
The following data were obtained during the first order thermal decomposition of $SO_2Cl_2$ at a constant volume:
$SO_2Cl_2(g) \rightarrow SO_2(g) + Cl_2(g)$
Calculate the rate constant.
$($Given: $\log4 = 0.6021, \log2 = 0.3010).$
View full solution →$SO_2Cl_2(g) \rightarrow SO_2(g) + Cl_2(g)$
|
Experiment
|
$Time/s^{–1}$
|
Total pressure/atm
|
| $1$ | $0$ | $0.4$ |
| $2$ | $100$ | $0.7$ |
$($Given: $\log4 = 0.6021, \log2 = 0.3010).$
How is the concept of coupling reactions useful in explaining the occurrence of non spontaneous thermochemical reactions? Explain giving an example.
A certain reaction is $50\%$ complete in $20$ minutes at $300 K$ and the same reaction is again $50\%$ complete in $5$ minutes at $350 K.$ Calculate the activation energy if it is a first order reaction. $\ce{[R = 8.314 JK^{-1}mol^{-1}, \log 4 = 0.602]}.$
View full solution →For the first order thermal decomposition reaction, the following data were obtained: $\text{C}_{2}\text{H}_{5}\text{Cl}\text{(g)}\rightarrow \text{C}_{2}\text{H}_{4}\text{(g)} + \text{HCl}\text{(g)} $
Calculate the rate constant $($Given: $\ce{\log 2 = 0.301, \log 3=0.4771, \log 4 =0.6021)}$
View full solution →| Time/$\sec$ | Total pressure$/\ce{atm}$ |
| $0$ | $0.30$ |
| $300$ | $0.50$ |
A first order reaction takes 20 minutes for 25% decomposition. Calculate the time when 75% of the reaction will be completed. (Given : log 2 = 0·3010, log 3 = 0·4771, log 4 = 0·6021)
The following data were obtained during the first order thermal decomposition of $SO_2Cl_2$ at a constant volume:
$\ce{SO_2Cl_2(g) \rightarrow SO_2(g) + Cl_2(g)}$
Calculate the rate constant.
$($Given: $\ce{log4 = 0.6021, log2 = 0.3010).}$
View full solution →$\ce{SO_2Cl_2(g) \rightarrow SO_2(g) + Cl_2(g)}$
|
Experiment
|
Time/s$^{–1}$
|
Total pressure/atm
|
| $1$ | $0$ | $0.4$ |
| $2$ | $100$ | $0.7$ |
$($Given: $\ce{log4 = 0.6021, log2 = 0.3010).}$
For a first order reaction$, A \rightarrow$ Products$, \text{k}=\frac{2.303}{\text{t}}\log\frac{\text{a}}{\text{a}-\text{x}},$ where a is the initial concentration of $A$ and $(a - x)$ is the concentration of $A$ after time $t. k$ is rate constant. Its value is constant at constant temperature for a reaction. The time in which half of the reactant is consumed is called half$-$life period. Half$-$life period of a first order reaction is constant. Its value is independent of initial concentration or any other external conditions.In these questions $(Q.$ No. $i-iv),$ a statement of assertion followed by a statement ofreason is given. Choose the correct answer out of the following choices.
View full solution →- Assertion and reason both are correct statements and reason is correct explanation for assertion.
- Assertion and reason both are correct statements but reason is not correct explanation for assertion.
- Assertion is correct statement but reason is wrong statement.
- Assertion is wrong statement but reason is correct statement.
- Assertion : Rate of reaction doubles when concentration of reactant is doubled if it is a first order reaction.
- Assertion : For the first order reaction, half$-$life period is expressed as $\text{t}_\frac{1}{2}=\frac{2.303}{\text{k}}\log2.$
- Reason : The half$-$life time of a first order reaction is not always constant and it depends upon the initial concentration of reactants.
- Assertion : For a first order reaction, the concentration of the reactant decreases exponentially with time.
- Assertion : Half$-$life period for a first order reaction is independent of initial concentration of the reactant.
The half$-$life of a reaction is the time required for the concentration of reactant to decrease by half, i.e.,
$[\text{A}]_\text{t}=\frac{1}{2}[\text{A}]$
For first order reaction,
$\text{t}_\frac{1}{2}=\frac{0.693}{\text{k}}$
this means $\text{t}\frac{1}{2}$ is independent of initial concentration. Figure shows that typical variation of concentration of reactant exhibiting first order kinetics. It may be noted that though the major portion of the first order kinetics may be over in a finite time, but the reaction will never cease as the concentration of reactant will be zero only at infinite time.
The following questions are multiple choice questions. Choose the most appropriate answer:
View full solution →$[\text{A}]_\text{t}=\frac{1}{2}[\text{A}]$
For first order reaction,
$\text{t}_\frac{1}{2}=\frac{0.693}{\text{k}}$
this means $\text{t}\frac{1}{2}$ is independent of initial concentration. Figure shows that typical variation of concentration of reactant exhibiting first order kinetics. It may be noted that though the major portion of the first order kinetics may be over in a finite time, but the reaction will never cease as the concentration of reactant will be zero only at infinite time.
The following questions are multiple choice questions. Choose the most appropriate answer:
- A first order reaction has a rate constant $k = 3.01 \times 10^{-3} /s$. How long it will take to decompose half of the reactant?
- $2.303s$
- $23.03s$
- $230.3s$
- $2303s$
- The rate constant for a first order reaction is $7.0 \times 10^{-4} s^{-1}$. If initial concentration ofreactant is $0.080 M,$ what is the half life of reaction?
- $990s$
- $79.2s$
- $12375s$
- $10.10 \times 10^{-4}s$
- For the half$-$life period of a first order reaction, which one of the following statements is generally false?
- It is independent of initial concentration.
- It is independent of temperature.
- It decreases with the introduction of a catalyst.
- None of these.
- The rate of a first order reaction is $0.04\ mol\ L^{-1} s^{-1}$ at $10$ minutes and $0.03\ mol\ L^{-1}\ s^{-1}$ at $20$ minutes after initiation. The half$-$life of the reaction is :
- $4.408$ min
- $44.086$ min
- $24.086$ min
- $2.408$ min
- The plot of $\text{t}_\frac{1}{2}$ vs initial concentration $[A]_0$ for a first order reaction is given by :
For a reaction, $A + B \rightarrow$ Products, the rate law is $-$ Rate $= k[A][B]^{3/2}$ Can the reaction be an elementary reaction? Explain.
View full solution →Decrease in concentration of reactant or increase in concentration of product per unit time is called rate of reaction. lt is of two types :
where$, dC =$ infinitely small change in concentration
$dt =$ infinitely small change in time.
For a reaction of the type$, m_1A + m_2B \rightarrow n_1C + n_2D$
Rate of reaction is given as
$\frac{1}{\text{m}_1}\frac{\text{d[A]}}{\text{dt}}=-\frac{1}{\text{m}_2}\frac{\text{d[B]}}{\text{dt}}=+\frac{1}{\text{n}_1}\frac{\text{d[C]}}{\text{dt}}=+\frac{1}{\text{n}_2}\frac{\text{d[D]}}{\text{dt}}$
In these questions $(Q.$ No. $i-iv),$ a statement of assertion followed by a statement ofreason is given. Choose the correct answer out of the following choices.
View full solution →- Instantaneous rate of reaction : Rate of change of concentration of reactant or product at a particular time is called instantaneous rate of reaction.
where$, dC =$ infinitely small change in concentration
$dt =$ infinitely small change in time.
- Average rate of reaction : Ratio of change in concentration and time required for the change is average rate of reaction.
For a reaction of the type$, m_1A + m_2B \rightarrow n_1C + n_2D$
Rate of reaction is given as
$\frac{1}{\text{m}_1}\frac{\text{d[A]}}{\text{dt}}=-\frac{1}{\text{m}_2}\frac{\text{d[B]}}{\text{dt}}=+\frac{1}{\text{n}_1}\frac{\text{d[C]}}{\text{dt}}=+\frac{1}{\text{n}_2}\frac{\text{d[D]}}{\text{dt}}$
In these questions $(Q.$ No. $i-iv),$ a statement of assertion followed by a statement ofreason is given. Choose the correct answer out of the following choices.
- Assertion and reason both are correct statements and reason is correct explanation for assertion.
- Assertion and reason both are correct statements but reason is not correct explanation for assertion.
- Assertion is correct statement but reason is wrong statement.
- Assertion is wrong statement but reason is correct statement.
- Assertion: The kinetics of the reaction, $\text{mA}+\text{nB}+\text{pC}\rightarrow\text{m}'\text{ X}+\text{n}'\text{ Y}+\text{p}'\text{ Z}$ obey the rate expression as $\frac{\text{dx}}{\text{dt}}=\text{k}[\text{A}]^\text{m}[\text{B}]^\text{n}.$
- Assertion : Instantaneous rate of reaction is equal to $\frac{\text{dx}}{\text{dt}}.$
- Assertion : For the reaction, $\text{RCl}+\text{NaOH}\rightarrow\text{ROH}+\text{NaCl},$ the rate of reaction is reduced to half on reducing the concentration of $\ce{RCl}$ to half.
- Assertion : ln rate law, unlike in the expression for equilibrium constants, the exponents for concentrations do not necessarily match the stoichiometric coefficients.
- Assertion : ln a reaction$, 2A + B \rightarrow A_2B,$ the reactant $B$ will disappear at twice the rate as $A$ will decrease.
The following reaction, $\text{A}_{(\text{g})}\xrightarrow{\ \ \triangle\ \ \ }\text{P}_{(\text{g})}+\text{Q}_{(\text{g})}+\text{R}_{(\text{g})},$ follows first order kinetics. The half$-$life period of this reaction is $69.3s$ at $500^\circ C$. The gas $A$ is enclosed in a container at $500^\circ C$ and at a pressure of $0.4$ atm.
The following questions are multiple choice questions. Choose the most appropriate answer :
View full solution →The following questions are multiple choice questions. Choose the most appropriate answer :
- The rate constant for the reaction is :
- $0.4s^{-1}$
- $0.02s^{-1}$
- $0.01s^{-1}$
- $0.3s^{-1}$
- The pressure of the gas $A$ after $230$ s will be :
- $0.04$ atm
- $0.36$ atm
- $0.4$ atm
- $0.036$ atm
- The total pressure of the system after $230$ swill be:
- $2.15$ atm
- $1.12$ atm
- $0.4$ atm
- $3.08$ atm
- The plot ofln$[A]$ vs twill be:
- Linear with slope $= k$
- Linear with intercept $= In[A]_0$
- Linear with slope $= In[A]_0$
- Linear with intercept $= [A]_0$
- Which of the following is not an example of first order reaction?
- $\text{C}_2\text{H}_{4(\text{g})}+\text{H}_{2(\text{g})}\rightarrow\text{C}_2\text{H}_{6(\text{g})}$
- $2\text{N}_2\text{O}_{5(\text{g})}\rightarrow4\text{NO}_{2(\text{g})}+\text{O}_{2(\text{g})}$
- $2\text{N}\text{H}_{3(\text{g})}\xrightarrow[\triangle]{\text{pt}}\text{N}_{2(\text{g})}+3\text{H}_{2(\text{g})}$
- $2\text{N}_2\text{O}_{(\text{g})}\xrightarrow{\ \ \triangle\ \ }2\text{N}_{2(\text{g})}+\text{O}_{2(\text{g})}$
The experimental data for decomposition of $\ce{N2O5}$
$[\ce{2N2O5 \rightarrow 4NO2 + O2}]$
in gas phase at $318K$ are given below :
View full solution →$[\ce{2N2O5 \rightarrow 4NO2 + O2}]$
in gas phase at $318K$ are given below :
| $t/s$ | $0$ | $400$ | $800$ | $1200$ | $1600$ | $2000$ | $2400$ | $2800$ | $3200$ |
| $10^2 \times [\ce{N2O5}]/mol\ L^{-1}$ | $1.63$ | $1.36$ | $1.14$ | $0.93$ | $0.78$ | $0.64$ | $0.53$ | $0.43$ | $0.35$ |
- Plot $[\ce{N2O5}]$ against $t$.
- Find the half$-$life period for the reaction.
- Draw a graph between $\log[\ce{N2O5}]$ and $t$.
- What is the rate law?
- Calculate the rate constant.
- Calculate the half$-$life period from $k$ and compare it with $(ii).$
The rate constant for the first order decomposition of $\ce{H_2O_2}$ is given by the following equation:
$\log k = 14.34 – 1.25 \times 10^4K/T$
Calculate $E_a$ for this reaction and at what temperature will its half$-$period be $256$ minutes?
View full solution →$\log k = 14.34 – 1.25 \times 10^4K/T$
Calculate $E_a$ for this reaction and at what temperature will its half$-$period be $256$ minutes?
The time required for $10\%$ completion of a first order reaction at $298K$ is equal to that required for its $25\%$ completion at $308K.$ If the value of $ A$ is $4 \times 10^{10}s^{–1}.$ Calculate $k$ at $318K$ and $E_a.$
View full solution →The rate constant for the decomposition of $\text{N_2O_5}$ at various temperatures is given below:
Draw a graph between ln $k$ and $1/T$ and calculate the values of $A$ and $E_a$. Predict the rate constant at $30^\circ$ and $50^\circ C.$
View full solution →| $T/^\circ C$ | $0$ | $20$ | $40$ | $60$ | $80$ |
| $105 \times k/s-1$ | $0.0787$ | $1.70$ | $25.7$ | $178$ | $2140$ |
The decomposition of a hydrocarbon follows the equation. $\text{k}=(4.5\times10^{11}\text{s}^{-1})\text{e}^{-28000}\text{ K/T}$
Calculate $Ea.$
View full solution →Calculate $Ea.$
(a) Define molecularity of the reaction-
(b) Explain the effect of the presence of a catalyst on the rate of reaction.
(c) In a first order reaction at 300 k the initial quantity of the reactant was $1.0 X ^{-2} molL ^{-1}$ which reduced to $0.5 \times 10^{-2} molL ^{-1}$ in 30 minutes Calculate the rate constant of the reaction at 300 k .
View full solution →(b) Explain the effect of the presence of a catalyst on the rate of reaction.
(c) In a first order reaction at 300 k the initial quantity of the reactant was $1.0 X ^{-2} molL ^{-1}$ which reduced to $0.5 \times 10^{-2} molL ^{-1}$ in 30 minutes Calculate the rate constant of the reaction at 300 k .
(a) In a chemical reaction rate constant almost doubles with the increase in temperature of $10^{\circ} C$ Explain with the help of a labelled distribution graph.
(b) The rate constant for a first order reaction is $60 Sec ^{-1}$ How long will it take for a Substance to become one sixteenth of its concentration.
View full solution →(b) The rate constant for a first order reaction is $60 Sec ^{-1}$ How long will it take for a Substance to become one sixteenth of its concentration.
The rate of reaction of exothermic reaction is _____________ with the increase in temperature.
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