CBSE Questions for Class 12 Engineering Chemistry Chemical Kinetics Quiz 10 - MCQExams.com

In the reaction, $$2N_2O_5\rightarrow 4NO_2+O_2$$, initial pressure is $$500\ atm$$ and rate constant $$k$$ is $$3.38\times 10^{-5} sec^{-1}$$. After 10 minutes the final pressure of $$N_2O_5$$ is:
  • 490 atm
  • 250 atm
  • 480 atm
  • 420 atm
$$A(g)\rightarrow B(g)+C(g)$$

$$\dfrac {-d[A]}{dt}=k[A]$$

 At the start, the pressure is 100 mm and after 10 min, the pressure is 120 mm. Hence, rate constant $$(min^{-1})$$ is:
  • $$\dfrac {2.303}{10} log (\dfrac {120}{100})$$
  • $$\dfrac {2.303}{10} log (\dfrac {100}{20})$$
  • $$\dfrac {2.303}{10} log (\dfrac {100}{80})$$
  • $$\dfrac {2.303}{10} log( \dfrac {100}{120})$$
For the $$1^{st}$$ order reaction: $$A_{(g)}\rightarrow 2B_{(g)}+C_{(s)}$$, the value of $$t_{\frac {1}{2}}=24\ mins$$. The reaction is carried out by taking a certain mass of $$A$$ enclosed in a vessel in which it exerts a pressure of $$400\ mm\ Hg$$. The pressure of the reaction mixture after the expiry of $$48\ mins$$ will be:
  • $$700\ mm$$
  • $$600\ mm$$
  • $$800\ mm$$
  • $$1000\ mm$$
In the first order reaction the concentration of reactant decreases from $$1.0\ M$$ to $$0.25\ M$$ in $$20$$ minutes. The value of specific rate is:
  • $$69.32$$
  • $$6.932$$
  • $$0.6932$$
  • $$0.06932$$
Calculate the half-life of the first-order reaction, $$C_2H_4O(g)\rightarrow CH_4(g)+CO(g)$$, if the initial pressure of $$C_2H_4O(g)$$ is 80 mm and the total pressure at the end of 20 minutes is 120 mm.
  • 40 min
  • 120 min
  • 20 min
  • 80 min
A reaction that is of the first order with respect to reactant A has a rate constant 6 min$$^{-1}$$. If we start with [A]=0.5 mol L$$^{-1}$$, when would [A] reach the value of 0.05 mol L$$^{-1}$$?
  • 0.384 min
  • 0.15 min
  • 3 min
  • 3.84 min
For the first order reaction $$A_{(g)}\rightarrow 2B_{(g)}+C_{(g)}$$, the initial pressure is $$P_A=90 mm$$ Hg, the pressure after 10 minutes is found to be 180 mm Hg. The rate constant of the reaction is:
  • $$1.15\times 10^{-3} sec^{-1}$$
  • $$2.3\times 10^{-3} sec^{-1}$$
  • $$3.45\times 10^{-3} sec^{-1}$$
  • $$6\times 10^{-3} sec^{-1}$$
The rate constant $$(k)$$ of a first-order reaction is $$0.0693\ min^{-1}$$. If we start with $$20\ mol\ L^{-1}$$, then it is reduced to $$2.5\ mol\ L^{-1}$$ in:
  • $$10\ mins$$
  • $$20\ mins$$
  • $$30\ mins$$
  • $$40\ mins$$
A certain zero order reaction has $$k=0.025\ M sec^{-1}$$ for the disappearance of A. What will be the concentration of A after 15 seconds if initial concentration is 0.5 M?
  • $$0.5 \ M$$
  • $$0.32 \ M$$
  • $$0.125 \ M$$
  • $$0.06 \ M$$
In the first order reaction, the concentration of the reactant is reduced to 25% in one hour.The half-life period of the reaction is:
  • 2 hr
  • 4 hr
  • 1/2 hr
  • 1/4 hr
In the following gaseous phase first order reaction
$$A(g)  \rightarrow 2 B(g) + C(g)$$
initial pressure was found to be $$400$$ mm of $$Hg$$ and it changed to $$1000$$ mm of $$Hg$$ after $$20$4 min. Then:
  • half life for $$A$$ is $$10$$ min
  • rate constant is $$0.0693$$ min$$^{-1}$$
  • partial pressure of $$C$$ at $$30$$ min is $$350$$ mm of $$Hg$$
  • total pressure after $$30$$ min is $$1100$$ mm of $$Hg$$
For a 1$$^{st}$$ order reaction (gaseous) (constant V, T) $$a A   \rightarrow (b - 1) B + 1 C$$ (with b > a) the pressure of the system rose by $$50 \left ( \frac{b}{a} - 1 \right )$$% in a time of 10 min. The half life of the reaction is therefore:
  • 10 min
  • 20 min
  • 30 min
  • 40 min
The half-period T for the decomposition of ammonia on tungsten wire was measured for different initial pressures P of ammonia at 25$$^o$$C. Then:
P(mm Hg)11214873120
T(sec)4892210320525
  • Zero order reaction
  • First order reaction
  • Rate constant for reaction is 0.114 mol lit$$^{-1}$$ sec$$^{-1}$$
  • Rate constant for reaction is 1.14 seconds
The energy of activation for the backward reaction is :


113108.jpg
  • $$30 kJ mol^{-1}$$
  • $$20 kJ mol^{-1}$$
  • $$10 kJ mol^{-1}$$
  • $$40 kJ mol^{-1}$$
Which of the following statements about zero order reaction is/are not true?
  • Unit of rate constant is $$sec^{-1}$$.
  • The graph between log (reactant) versus time is a straight line.
  • The rate of reaction increases with the increase in concentration of reactants.
  • Rate of reaction is independent of concentration of reactants.
Which of the following reactions is/are of the first order?
  • The decomposition of ammonium nitrate in an aqueous solution.
  • The inversion of cane-sugar in the presence of an acid.
  • The acidic hydrolysis of ethyl acetate.
  • All radioactive decays.
For the first order reaction, $$A(g)\rightarrow 2B(g)+C(g)$$, the initial pressure is $$P_A=90$$ mm Hg. Then pressure after 10 minutes is found to be 180 mm Hg. The half-life period of the reaction is:
  • $$1.15\times 10^{-3} sec^{-1}$$
  • $$600\;sec$$
  • $$3.45\times 10^{-3} sec^{-1}$$
  • $$200\;sec$$
The initial rate of zero-order reaction of the gaseous equation $$A$$ (g) $$\rightarrow$$ $$2B$$ (g) is 10$$^{-2}$$ M min$$^{-1}$$ if the initial concentration of $$A$$ is 0.1 M. What would be a concentration of $$B$$ after $$60$$ seconds?
  • $$0.09 M$$
  • $$0.01 M$$
  • $$0.02 M$$
  • $$0.03 M$$
In 20 minutes of 80% of $$N_2O_5$$ is decomposed. Rate constant is:

113102.jpg
  • 0.08
  • 0.05
  • 0.12
  • 0.2
The inactivation of a viral preparation in a chemical bath is found to be a first-order reaction. The rate constant for the viral inactivation per minute, if in the beginning $$1.5\%$$ of the virus is inactivated, is:
  • $$1.25\times 10^{-4}\ sec^{-1}$$
  • $$2.5\times 10^{-4}\ sec^{-1}$$
  • $$5\times 10^{-4}\ sec^{-1}$$
  • $$2.5\times 10^{-4}\ min^{-1}$$
A certain substance A is mixed with an equimolar quantity of substance B. At the end of an hour, A is 75% reacted. Calculate the time when A is 10% unreacted. (Given: order of reaction is zero)
  • 1.2 hr
  • 1.8 hr
  • 2.0 hr
  • 2.4 hr
A drug was known to be effective after it has decomposed 30 %. The original concentration of a sample was 500 units/ml. When analyzed 20 months later, the concentration was found to be 420 units/ml. Assuming that decomposition is of Ist order, what will be the expiry time of the drug?
  • 41 months
  • 40 months
  • 35 months
  • 38 months
The rate constant for disappearance of reactant as mentioned in is $$\displaystyle 2 \times 10^{-2} mol L^{-1} sec^{-1}$$, if the concentration of the reactant after 25 sec is 0.25M, the initial concentration is:
  • 0.75 M
  • 0.89 M
  • 1.03 M
  • 1.46 M
A first order reaction is 20% complete in 10min. The specific rate constant is:
  • 0.0223 $$min^{-1}$$
  • 0.0423 $$min^{-1}$$
  • 0.0501 $$min^{-1}$$
  • 0.0517 $$min^{-1}$$
For the first order homogeneous gaseous reaction $$A\rightarrow 2B+C$$, the initial pressure was $$P_i$$ while total pressure at time 't' was $$P_t$$. Write expression for the rate constant k in terms of $$P_i, P_t$$ & $$t$$.
  • $$k=\cfrac {2.303}{t}log \left (\cfrac {2P_i}{3P_i-P_t}\right )$$
  • $$k=\cfrac {2.303}{t}log \left (\cfrac {2P_i}{ 2P_t-P_i}\right )$$
  • $$k=\cfrac {2.303}{t}log \left (\cfrac {P_i}{P_i-P_t}\right )$$
  • None of these
A viral preparation was inactivated in a chemical bath. The inactivation process was found to be first order in virus concentrations. At the beginning of the experiment, 2.0% of the virus was found to be inactivated per minute. The k for inactivation process is:
  • $$3\times10^{-4} s^{-1}$$
  • $$4\times10^{-4} s^{-1}$$
  • $$5\times10^{-4} s^{-1}$$
  • $$6\times10^{-4} s^{-1}$$
A solution of $$A$$ is mixed with an equal volume of a solution of $$B$$ containing the same number of moles, and the reaction $$A+B \longrightarrow C$$ occurs. At the end of 1 hour, $$A$$ is $$75$$% reacted. The amount of $$A$$ that will be left unreacted at the end of $$2$$ hours if the reaction is first order in $$A$$ and zero order in $$B$$ is:
  • $$6.25$$
  • $$7.28$$
  • $$8.43$$
  • $$8.92$$
For the following data for the zero order reaction $$A\rightarrow$$ products. Calculate the value of k. 
Time                    [A]
0.0                      0.10 M
1.0                      0.09 M
2.0                      0.08 M
  • $$k=0.01 \, M min^{-1} $$
  • $$k=0.03 \, M min^{-1} $$
  • $$k=0.06 \, M min^{-1} $$
  • $$k=0.08 \, M min^{-1} $$
The decomposition of $$ {\mathrm{N}_{2}}\mathrm{O}_{5} $$ according to the equation $${\mathrm{2N}_{2}}\mathrm{O}_{5}(g)\rightarrow \mathrm{4 NO}_{2}+O_{2}(g) $$ is a first-order reaction. After 30 min from the start of decomposition in a closed vessel the total pressure developed is found to be 284.5 mm Hg. On complete decomposition, the total pressure is 584.5 mm Hg. The rate constant of the reaction is :
  • $$\mathrm{k}_{1} =5.206\times10^{-3}\ \mathrm{min}^{-1}$$
  • $$\mathrm{k}_{1} =3.102\times10^{-3}\ \mathrm{min}^{-1}$$
  • $$\mathrm{k}_{1} =3.126\times10^{-3}\ \mathrm{min}^{-1}$$
  • $$\mathrm{k}_{1} =3.453\times10^{-3}\ \mathrm{min}^{-1}$$
The reaction is given below, the rate constant for disappearance of A is $$7.48\times10^{-3}sec^{-1}$$. The time required for the total pressure in a system containing A at an initial pressure of 0.1 atm to rise to 0.145 atm is:
$$2A(g)\rightarrow 4B(g)+C(g)$$
  • 0.80 min
  • 0.567 min
  • 0.433 min
  • 0.344 min
The reaction $$A(aq) \rightarrow B(aq)+C(aq)$$ is monitored by measuring optical rotation of reaction mixture at different time interval. The species A, B and C are optically active with specific rotations $$20^{\circ}, 30^{\circ}$$ and $$-40^{\circ} $$ respectively. Starting with pure A if the value of optical rotation was found to be $$2.5^{\circ}$$ after $$6.93^{\circ}$$ minutes and optical rotation was $$-5^{\circ}$$ after infinite time. Find the rate constant for the first-order conversion into A into B and C:
  • $$0.1 min^{-1}$$
  • $$0.2 min^{-1}$$
  • $$0.3 min^{-1}$$
  • $$0.4 min^{-1}$$
   Time t $$\infty $$
 Rotation of Glucose & Fructose  $$ r_{t}  $$ $$r _{\infty }$$ 
$$S\rightarrow$$ $$G+F  $$ 
What id the value of $$k$$ for the above reaction under given circumstances?
  • $$\displaystyle k=\frac{1}{t}ln\frac{r_{\infty }}{(r_{\infty }-r_{t})}$$
  • $$\displaystyle k=\frac{1}{t}ln\frac{r_{t}}{(r_{\infty }-r_{t})}$$
  • $$\displaystyle k=\frac{1}{t}ln\frac{r_{\infty }}{(r_{t}-r_{\infty})}$$
  • $$\displaystyle k=\frac{1}{t}ln\frac{r_{t}}{(r_{t}-r_{\infty})}$$
A metal slowly forms an oxide film which completely protects the metal when the film thickness is 3.956 thousandths of an inch. If the film thickness is 1.281 thou. in 6 weeks, then the time it will take before it is 2.481 thou. is :(the rate of film formation follows first-order kinetics)
  • 12 weeks
  • 14 weeks
  • 15 weeks
  • 17 weeks
At $$100^{\circ}$$C the gaseous reaction $$A\rightarrow $$2B+C was observed to be of first order. On starting with pure A it is found that at the end of 10 minutes the total pressure of system is 176mm.Hg and after a long time 270mm Hg.
Initial pressure of A is:
  • 90mm
  • 80mm
  • 70mm
  • 60mm
For a reversible first - order reaction $$A\rightleftharpoons B K_{1}=10^{-2}s^{-1}$$ and $$[B]_{eq}=4$$. If $$[A]_{0}=0.01$$ mole $$L^{-1} $$ and $$ [B]_{0}=0$$, what will be the concentration of B after 30 s?
  • 0.0025 m
  • 0.0013 m
  • 0.0026 m
  • 0.0030 m
In this case, we have (Consider it as a first-order reaction)
                    $$A\rightarrow B+C$$
Time                  $$t$$                 $$\infty $$
Total pressure  $$ p_{2}$$          $$             \ \ \:\:\:\:p_{3}$$
Then $$k$$ is:
  • $$\displaystyle k=\frac{1}{t}ln\frac{p_{3}}{2(p_{3}-p_{2})}$$
  • $$\displaystyle k=\frac{1}{t}ln\frac{p_{2}}{2(p_{3}-p_{2})}$$
  • $$\displaystyle k=\frac{1}{t}ln\frac{p_{3}}{2(p_{1}-p_{2})}$$
  • $$\displaystyle k=\frac{1}{t}ln\frac{p_{1}}{2(p_{3}-p_{2})}$$
$$\displaystyle SO _{2}Cl _{2}(g)\rightarrow SO_{2}(g)$$ 

The given reaction is a first order gas reaction with $$k=2.2 \times \displaystyle 10^{-5}sec^{-1}$$ at $$ 320^{\circ}$$C. What % of $$SO_{2}Cl_{2}$$ is decomposed on heating this gas for 90 min?
  • 11.2%
  • 12.3%
  • 13.4%
  • 14.5%
The decomposition of a compound $$P$$, at temperature $$T$$ according to the equation $$\displaystyle2P_{(g)}\rightarrow4Q_{(g)}+R_{(g)}+S_{(l)}$$ is the first order reaction. After $$30$$ minutes from the start of decomposition in a closed vessel, the total pressure developed is found to be $$317$$ mm $$Hg$$ and after a long period of time the total pressure observed to be $$617$$ mm $$Hg$$. 
The total pressure of the vessel after $$75$$ minute, if the volume of liquid $$S$$ is supposed to be negligible is:
(Given : Vapour pressure of $$S (l)$$ at temperature $$T=32.5 $$mm $$Hg$$)
  • $$P_{t}=379.55$$ mm $$Hg$$
  • $$P_{t}=387.64$$ mm $$Hg$$
  • $$P_{t}=468.23$$ mm $$Hg$$
  • $$P_{t}=489.44$$ mm $$Hg$$
$$A(aq)\longrightarrow B(aq)+C(aq)$$ is a first order reaction.
Time
$$t$$
$$\infty$$
moles of reagent
$${ n }_{ 1 }$$
$${ n }_{ 2 }$$
Reaction progress is measure with help of titration '$$R$$'. If all $$A,B$$ and $$C$$ reacted with reagent and have '$$n$$' factors [$$n$$ factor; $$eq.wt=\cfrac {mol.wt.}{n}$$] in the ratio of $$1:2:3$$ with the reagent. The $$k$$ in terms of $$t,{ n }_{ 1 }$$ and $${ n }_{ 2 }$$ is :
  • $$k=\cfrac { 1 }{ t } \ln { \left( \cfrac { { n }_{ 2 } }{ { n }_{ 2 }-{ { n }_{ 1 } } } \right) } $$
  • $$k=\cfrac { 1 }{ t } \ln { \left( \cfrac { 2{ n }_{ 2 } }{ { n }_{ 2 }-{ { n }_{ 1 } } } \right) } $$
  • $$k=\cfrac { 1 }{ t } \ln { \left( \cfrac {4 { n }_{ 2 } }{ { n }_{ 2 }-{ { n }_{ 1 } } } \right) } $$
  • $$k=\cfrac { 1 }{ t } \ln { \left( \cfrac {4 { n }_{ 2 } }{5( { n }_{ 2 }-{ { n }_{ 1 }) } } \right) } $$
Two first order reaction have half-lives in the ratio $$8:1$$. Calculate the ratio of time intervals $${ t }_{ 1 }$$ and $${ t }_{ 2 }$$ are the time period for the $${ \left( \cfrac { 1 }{ 4 }  \right)  }^{ th }$$ and $${ \left( \cfrac { 3 }{ 4 }  \right)  }^{ th }$$ completion.
  • $$1:0.301$$
  • $$0.125:0.602$$
  • $$1:0.602$$
  • none of these
The gaseous decomposition reaction, $$A(g)\longrightarrow 2B(g)+C(g)$$ is observed to first order the excess of liquid water at $${ 25 }^{ o }C$$. It is found that after $$10$$ minutes the total pressure of system is $$188$$ torr and after very long time it is $$388$$ torr. The rate constant of the reaction (in $$hr^{ -1 }$$) is:
[Given: vapour pressure of $${ H }_{ 2 }O$$ at $${ 25 }^{ o }C$$ is $$28$$ torr. ($$\ln { 2 } =0.7,\ln { 3 } =1.1,\ln { 10 } =2.3$$)]
  • $$0.02$$
  • $$1.2$$
  • $$0.2$$
  • none of these
A compound $$A$$ dissociate by two parallel first order paths at certain temperature
$$A(g)\xrightarrow [  ]{ { k }_{ 1 }({ min }^{ -1 }) }  2B(g)$$  $${ k }_{ 1 }=6.93\times { 10 }^{ -3 }min^{ -1 }$$
$$A(g)\xrightarrow [  ]{ { k }_{ 2 }({ min }^{ -1 }) }  C(g)$$  $${ k }_{ 2 }=6.93\times { 10 }^{ -3 }min^{ -1 }$$
The reaction started with $$1$$ mole of pure '$$A$$' in $$1$$ litre closed container with initial pressure $$2$$ atm. What is the pressure (in atm) developed in container after $$50$$ minutes from start of experiment?
  • $$1.25$$
  • $$0.75$$
  • $$1.50$$
  • $$2.50$$
For a first-order homogeneous gaseous reaction, $$A\longrightarrow 2B+C$$.
If the total pressure after time $$t$$ was $${ P }_{ t }$$ and after long time $$(t\rightarrow \infty )$$ was $${ P }_{ \infty }$$ then $$k$$ in terms of $${ P }_{ t },{ P }_{ \infty }$$ and $$t$$ is :
  • $$k=\cfrac { 2.303 }{ t } \log { \left( \cfrac { 2{ P }_{ \infty } }{ { P }_{ \infty }-{ P }_{ t } } \right) } $$
  • $$k=\cfrac { 2.303 }{ t } \log { \left( \cfrac { 2{ P }_{ \infty } }{2( { P }_{ \infty }-{ P }_{ t }) } \right) } $$
  • $$k=\cfrac { 2.303 }{ t } \log { \left( \cfrac {2 { P }_{ \infty } }{3( { P }_{ \infty }-{ P }_{ t }) } \right) } $$
  • none of these
The reaction $$A(g)\longrightarrow B(g)+2C(g)$$ is a first order reaction with rate constant $$2.772\times { 10 }^{ -3 }s^{ -1 }$$. Starting with $$0.1$$ mole of $$A$$ in $$2$$ litre vessel, find the concentration of $$A$$ after $$250sec$$ when the reaction is allowed to take place at constant pressure at $$300K$$? (Given ln2= 0.693)
  • $$0.0125M$$
  • $$0.025M$$
  • $$0.05M$$
  • none of these
$$\displaystyle \:A+B\rightleftharpoons AB+I\xrightarrow{k_{2}}P+A$$
If $$k_1$$ is the rate constant of the reversible step and If $$k_1$$is much smaller than $$k_{2}$$, The most suitable qualitative plot of potential energy (P.E.) versus reaction coordinate for the above reaction.
Assertion: In a reversible endothermic reaction, $$E_{act}$$ of forward reaction is higher than that of backward reaction.
Reason: The threshold energy of forward reaction is more than that of backward reaction.
  • Both Assertion and Reason are true and Reason is the correct explanation of Assertion
  • Both Assertion and Reason are true but Reason is not the correct explanation of Assertion
  • Assertion is true but Reason is false
  • Assertion is false but Reason is true
  • Both Assertion and Reason are false
The reaction  $$cis-X\overset { { k }_{ f } }{ \underset { { k }_{ b } }{ \rightleftharpoons  }  }  tran-X$$ is first order in both directions. At $${ 25 }^{ o }C$$, the equilibrium constant is $$0.10$$ and the rate constant $$ { k }_{ f }=3\times { 10 }^{ -4 }s^{ -1 }$$. In an experiment starting with the pure $$cis-$$form, how long would it take for half of the equilibrium amount of the $$trans-$$ isomer to be formed?
  • $$150$$sec
  • $$200$$sec
  • $$155$$sec
  • $$210$$sec
For a given reaction of the first order, it takes 15 minutes for the concentration to drop from 0.8 M to 0.4 M. The time required for the concentration to drop from 0.1 M to 0.025 M will be :
  • 15 minutes
  • 60 minutes
  • 30 minutes
  • 7.5 minutes
The study of chemical kinetics becomes highly complicated if there occurs:
  • reversible reaction
  • side reaction
  • surface reaction
  • none of these
A reaction occurs in parallel paths. For each path having energy of activation as $$E,\ 2E,\ 3E,\ ... nE$$ and rate constant $$K,\ 2K,\ 3K,\ .... nK$$ respectively. If $$E_{AV}=3E$$, then find out the value of $$n$$.
  • $$4$$
  • $$5$$
  • $$6$$
  • None of these
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