Explore topic-wise InterviewSolutions in Current Affairs.

This section includes 7 InterviewSolutions, each offering curated multiple-choice questions to sharpen your Current Affairs knowledge and support exam preparation. Choose a topic below to get started.

1.

Rateof a reaction

Answer»

increases withincreasesin temperature
decreaseswithincreases in temperature
doesnotdependontemperature
Doesnotdependon CONCENTRATION

Solution :Increase in termperaturefavoursfavourscollisionof MOLECULES
2.

Rate of a reaction :

Answer»

INCREASES with INCREASE in TEMPERATURE
Decreases with increase in temperature
Does not DEPEND on temperature
Does not depend on concentration

Answer :A
3.

Rate of a chemical reactiondependson concentrationof reactant isindependenton concentration. Why?

Answer»

Solution :ACCORDING to law of mass action rate of a REACTION is proportional to the concentration of each reactant involved in the reaction.
Rate constant is the rate of reaction at unit concentration of each reactant. HENCE rate constant is independent of CONCENTRATIONS of reactants.
Therefore rate is dependent and rate constant is independent on the concentration.
4.

Rate of a chemical reaction can be kept constant by

Answer»

stirring the compounds
keeping the temperature constant
both (a) and (b)
NONE of these

Solution :The rate of REACTION depends UPON conc. of REACTANT, surface area of reactant, PRESSURE, temperature, presence of light and catalyst.
5.

Rate of a chemical reaction 2A (g) to B(g) is defined as : 'r_B'=1/V(dn_B)/(dt) Where n_B=number of moles of B formed and C_B =Concentration of B then which of the following relation correct .

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`r_B=(dC_B)/(dt)+(C_B)/V(DV)/(dt)` (If volume V is not CONSTANT )
`r_B=(dC_B)/(dt)`(If volume V is constant)
`r_B=(dC_B)/(dt)-(C_B)/V(dV)/(dt)` (If volume V is not constant )
`r_B=-(dC_B)/(dt)+(C_B)/V(dV)/(dt)` (If volume V is not constant )

SOLUTION :`r_B=(dC_B)/(dt)=1/V(dn_B)/(dt)=1/V(d(C_BV))/(dt)=V/V(dC_B)/(dt)+C_B/V(DV)/(dt)=(dC_B)/(dt)+C_B/V(dV)/(dt)`
6.

Rate of a chemical reaction can be kept constant by:

Answer»

STIRRING the compounds
Keeping the TEMPERATURE constant
Both (a) and (B)
None

Answer :B
7.

Rate law has to be determined __________ and cannot be predicted.

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SOLUTION :EXPERIMENTALLY
8.

Rate law for the reactionA+2B to 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 ________.

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the same
DOUBLED
QUADRUPLED
HALVED

ANSWER :B
9.

Rate law for the reaction A+2BtoC 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 ………………. .

Answer»

the same
doubled
quadrupled
halved

Solution :RATE constant of a REACTION does not depend upon CONCENTRATIONS of the REACTANTS.
10.

Rate law can not be determined from balanced chemical equation if ………………….. .

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reverse REACTION is involved
it is an ELEMENTARY reaction
it is a SEQUENCE of elementary REACTIONS
any of the reactants is in excess.

Answer :A::C::D
11.

Rate law for 2A+BtoC+D from following data: "S.No."""[A](M)""[B](M)"""Rate"(M//s) 1""0.01""0.01""2.5 2""0.01""0.02""5 3.""0.03""0.02""45

Answer»

`r=K[A]^(1//3)[B]`
`r=K[A]^(2)[B]`
`r=K[A][B]^(1//3)`
`r=K[A]^(2//3)[B]^(1//3)`

ANSWER :B
12.

Rate law cannot be determined from balanced chemical equation if ________

Answer»

Reverse reactions is not involved
It is an ELEMENTARY reaction
It is a sequence of elementary reactions
All of the reactants is in EXCESS. RATE LAW can be determined from balanced chemical equation if it is an elementary reaction.

Answer :C
13.

Rate law cannot be determined from balanced chemical equation if……

Answer»

reverse REACTION is involved
it is an elementary reaction
it is a sequence of elementary reactions
any of the REACTANTS is in excess.

Solution :Only for IRREVERSIBLE elementary reaction RATE law is directly obtained.
14.

Rate= k[NO]^(2) [O_(2)]^(1). By how many times does the rate of reaction change when the volume of the reaction vessel is reduced to 1//3^(rd) of its original volume ? Will ther he any change in the order of the reaction.

Answer»

Solution :`r_(1) = k[NO]^(2) [O_(2)]^(1), r_(2) = k[(NO)/(3)]^(2) [(O_(2))/(3)]^(1)`
`r_(2) = 27r_(1)` Rate of reaction increases by 27 TIMES
Order of the reaction REMAINS same.
15.

Rate expressionfor two reaction are : (a) "rate"_(a) = k_(a)[A] and (b) "rate"_(b) = k_(b) [B]^(2) . When[A] = [B] = 1 mol l^(-1) , k_(a) = k_(b) mol L^(-1). If [A] = [B] = 2 mol L^(-1) , write therelation between"rate"_(a)and "rate"_(b) .

Answer»

Solution :`"Rate"_(a)=k_(a)[2" mol L"^(-1)]`
`"Rate"_(B)=k_(b)["2 mol L"^(-1)]^(2)=k_(1)["2 mol L"^(-1)]^(2)`
The ration of the RATES of two REACTIONS (a) and (b) is given as, `("Rate"_(a))/("Rate"_(b))=(k_(a)["2 mol L"^(-1)])/(k_(a)["2 mol L"^(-1)]^(2))=1/2`
The ration of the rates = `1:2`.
16.

Rate law.

Answer»

Solution :It is defined as an EXPERIMENTALLY determined MATHEMATICAL equation which EXPRESSES the rate of a chemical reaction in terms of MOLAR concentrations of the reactants which influence the rate of the reaction.
17.

Rate if a reaction can be expressed by Arrhenius equations as : k = Ae^(-E//RT) In this equation , E represents

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The energy above which all the colliding MOLECULES will REACT
The energy below which colliding molecules will not react
The total energy of the reacting molecules at a temperature , T
The fractionof molecules with energy greater than the activation energy of the REACTION

Solution :None of the given options is PERFECTLY correct . The closest choice is option (b) .
18.

Rate expression of a chemical change is (dx)/(dt) =k[A]^1[B]^(1//2)[C]^(3//2). The order of the reaction is

Answer»

2
3
1
zero

Solution :Order of REACTION is sum of POWER raised on concentration terms in expression
RATE `= 1+1/2+3/2=3` Thus order `= 1+ 1/2 + 1/2=3`.
19.

Rate equation is the expression that gives the relation between rate of reaction and :

Answer»

Temperature
Concentration of products
Concentration of reactants
None of the above

Answer :C
20.

Rate expression for xA+yBto prodcuts is Rate =k[A]^(m)[B]^(n). Units of K with respect to A and B respectively are s^(-1) and M^(-1).s^(-1) when concentration of A and B are increased by 4 times, then

Answer»

`R_(F)=16R_(i)`
`R_(i)=16R_(f)`
`R_(f)=8R_(i)`
`R_(f)=64R_(i)`

ANSWER :D
21.

Rate equation for a second order reaction is :

Answer»

`K=(2.303)/TLOG((a)/(a-X))`
`K=(1)/tlog((a)/(a(a-x)))`
`K=(1)/t.(x)/(a(a-x))`
`K=(1)/t^2.(a)/((a-x))`

Answer :C
22.

Rate constnat K=2.303"min"^(-1) for a particular reactio the initial concentration of there reactant is 1 mole/litre then rate of reaction after 1 minute is

Answer»

`2.303M "min"^(-1)`
`0.2303 M "min"^(-1)`
0.1M "min"^(-1)`
NONE of these

Solution :`K=2.303/t "log"(C_(o))/(C_(t))`
`C_(t)=0.1`
RATE `=k_(1)[c_(t)]`
Rate `=0.2303M "min"^(-1)`
23.

Rate contant k_2 of a reaction at 310 Kis two time of its rate constant k_1at 300 K.Calculate activation energy of the reaction.(log 2=0.3010,log 1=0)

Answer»

SOLUTION :LOG `k_2/k_1=(EA)/(2.303R)((T_2-T_1)/(T_1T_2))`
LOG2=`(Ea)/(2.303xx8.314)[((310-300))/(310xx300)] Ea=(0.3010xx2.303xx8.314xx300)/10=53598J`
24.

Rate constant of a reaction (k) is 175 "litre"^(2)mol^(-2)sec^(-1). What is the order of reaction ?

Answer»

first
second
third
zero

Solution :( C ) : On the BASIS of GIVEN UNITS of k, the reaction is of 3rd order.
25.

Rate constant value depends on:

Answer»

Temperature
Time
Initial concentration
None of these

Answer :A
26.

Rate constant of a reaction is K=3.4 xx 10^-4 mol^-1 LS^-1 What is the order of the reaction ?

Answer»

SOLUTION :SECOND ORDER.
27.

Rateconstantof a reaction is 10^(-3) s^(-1). Calculatethepercentagecompletionof thereaction in .

Answer»


ANSWER :0.1821
28.

Rate constant of a reaction is k = 3.14 xx 10^(-4) mol L^(-1)s^(-1). What is the order of the reaction.

Answer»

SOLUTION :SECOND ORDER.
29.

Rate constant of a first order reaction is 6.93 xx 10^(-3) mi n^(-1). Calculate the half-life period.

Answer»

Solution :GIVEN `K = 6.93 xx 10^(-3) mi N^(-1)`
`t_(1/2) = `?
`t_(1/2) = 0.693/K = 0.693/6.93 xx 10^(-3)mi n^(-1) = 100 min`
30.

Rate constant of a reaction at 290K was found to be 3.2 xx 10^-3 . At 300K , it will be :

Answer»

`1.28xx10^-2`
`9.6xx10^-3`
`6.4xx10^-3`
`3.2xx10^-4`.

ANSWER :C
31.

Rate constant of a first order reaction at 298 K is 15.5 s^(-1). What is the approximate rate constant for this reaction at 308 K?

Answer»

Solution :The EXPECTED RATE CONSTANT for this REACTION is `31s^(-1)`.
32.

Rate constant of a first order reaction is 0.0693 min^(-1). Calculate the percentage of the reactant remaining at the end of 60 minutes.

Answer»

Solution :FORMULA : `K = (2.303)/(t) log""([R]_(0))/([R])`
` 0.0693 = (2.303)/(60) log""(100)/([R]) rArr 1.8 = log (100)/([R])`
ANTILOG `1.8 = (100)/([R])`
`63.1 = (100)/([R]) rArr [R] = 1.584%`
33.

Rate constant of a first order reaction A to B is 0.0693min^(-1). Calculate rate (i) at start and (ii) after 30 minutes. Initial concentration of A is 1.0M.

Answer»

Solution :`k=0.0693min^(-1)`
`t_((1)/(2))=(0.693)/(k_(1))=(0.693)/(0.0693)=10`min
Since `C=C_(@)((1)/(2))^(n)` `n=(t)/(t_(1//2))`
`n=(30)/(10)=3``C_(@)=1M`
`:.C=1xx((1)/(2))^(3)=(1)/(8)M`
Rate of the reaction at the START of the reaction `=k_(1)xxC_(@)`.
`=10xx0.0693xx1=0.693M min^(-1)`
Rate after `30`min `=k_(1)C=00693xx(1)/(8)=8.66xx10^(-8)M min^(-1)`
34.

Rate constant of a first order reaction A products is 0.016 min^(-1). Calculate the time required for 80% of the reaction to be completed.

Answer»

SOLUTION :`K = (2.303)/(t) LOG.(a)/(a-x)`
`t = (2.303)/(0.016)log.(100)/(100-80)`
`t = (2.303)/(0.016)log 5`
`t = 100.6 MIN`
35.

Rate constant of a 1st order reaction is 0.5 s^(-1).What is the half-life period ?

Answer»

SOLUTION :`t_(1//2)=0.693/K=(0.693/0.5)s=1.386s`
36.

Rate constant k of a reaction varies with temperature T according to the following Arrhenius equation. log k log A(E_a)/(2.303R)(1/T) where E_a is the activation energy . When a graph is plotted is or logk Vs 1/T a straight line with a slope of - 400K is obtained . Calculate the activation energy .

Answer»

SOLUTION :LOG k = log A - `E_a/(2.303R)(1/T)`
y = c + mx
`m=-E_a/(2.303R)`
`E_a=-2.303Rm`
`E_a=-2.303xx8.314"J K "^(-1)"MOL"^(-1)XX(-400K)`
`E_a=76,589"J mol"^(-1)`
`E_a = 76 589 "kJ mol"^(-1)` .
37.

Rate constant (k)of a reaction is 5xx10^(-2)s^(-1).Find the half life (t_(1/2)) of the reaction.

Answer»

SOLUTION :`t_(1/2)=0.693/5xx10^(-2)=13.86` SEC
38.

Rate constant K varies with temperature by equation log K("min"^(-1))=5-((2000))/T.We can conclude that (R=8.314J"mol"^(-1)K^(-1) (or) cal "mol"^(-1)K^(-1))

Answer»

Pre exponential factor A is 5
Ea is 4 K cal/mol
Pre exponential factor, A is `10^(5)`
Ea is 9.212 Kcal/mol

Solution :`K=A.e^(-Ea//RT),logK=logA-(epsilon_(a))/(2.303R)xx1/T`
`logA=5,A=10^(5),(E_(a))/(2.303RT)=2000/T,E_(a)=(2000xx2.303xx2)/1,E_(a)=9.212KCal`
39.

Rate constant 'k' of a reaction varies with temperature 'T' according to the equation: log k= logA-(E_(a))/(2.303R)((1)/(T)) where E_(a) is the activation energy. When a graph is plotted for log k vs (1)/(T), a straight line with a slope of -4250 K is obtained. Calculate 'E_(a)'for the reaction. [R=8.314JK^(-1)"mol"^(-1)]

Answer»

SOLUTION :The equation
`log k=log A -(E_(a))/(2.303R) ((1)/(T))`
is of the type `y=mx +C` where m is the slope of the line.
`therefore (-E_(a))/(2.303R)= -4250 K or E_(a)=2.303R xx 4250 K`
or`E_(a)=2.303xx 8.314 JK^(-1)"MOL"^(-1) xx 4250K`
`=81375"J mol"^(-1)=81.375 "kJ mol"^(-1)`
40.

Rate constant k for first order reaction has been found to be 2.54xx10^(-3)s^(-1). Calculate its three-fourth time.

Answer»

Solution :For the first ORDER reaction, use the relation
`k=(2.303)/(t)"log"([R]_(0))/([R])`
For three-foursth of the reaction to take place, `[R]=([R]_(0))/(4)or ([R]_(0))/([R])=4`
Substituting the values in the rate equation, we have
`2.54xx10^(-3)=(2.303)/(t)LOG4`
or `t=(2.303)/(2.54)xx10^(3)xx0.6021=5.46xx10^(2)s`
41.

Rate constant (k) for x Ato products is 0.04" M - min"^(-1). When [A] changes form 0.08 M to 0.02M, ratio of initial to final rate is

Answer»

`1//4`
`1//16`
1
4

Answer :C
42.

The rate constant 'k'. For a reaction varies with temperature 'T' according to the question. log k = log A-(E_(a))/(2.303R)(1/T) Where E_(a) is the activation energy. When a graph is plotted for log k vs 1//T, a straight line with a slope of -4250 K is obtained. Calcualte E_(a) for this reaction.

Answer»

SOLUTION :SLOPE =`E_a/(2.303R)`=-4250 K
So, `E_a=-2.303xxRxx"Slope"`
`=-2.303xx8.314 J K^(-1) "mol"^(-1) xx4250`
`=81375.3 "J mol"^(-1)`
`=81.375 "KJ mol"^(-1)`
43.

Rate constant k for a reaction varies with temperature according to the equation log k ="constant"-(E_(a))/(2.303R)*(1)/(T) where E_(a) is the energy of activation for the reaction. When a graph is plotted for log k vs 1//T, a straight line with a slope of -6670 K is obtained. Calculate energy of activation for this reaction. State the units. ""[R=8.314JK^(-1)"mol"^(-1)]

Answer»

Solution :The following data is provided
SLOPE `= -6670K, R=8.314 JK^(-1)"mol"^(-1)`
Slope `= -(E_(a))/(2.303R) or E_(a)= -"Slope" xx 2.303 xx R`
SUBSTITUTING the VALUES, we have
`E_(a)= -(-6670)K xx 2.303 xx 8.314JK^(-1)"mol"^(-1)=+127.714"KJ mol"^(-1)`
44.

Rate constant for the decomposition of ethylene oxide into CH_(4) and CO may be described by the equation logl(s^(-1))=14.34-(1.25xx10^(4))/(T) (a) What is the energy of activation of this reaction ? (b) What is the value of k at 670K ?

Answer»

SOLUTION :`(a) 239.34kj MOL^(-1)` `(B) 4.82xx10^(-5)s^(-1)`
45.

Rate constant for a reaction varies with temperature as, ln K(sec^(-1))=14.34-(1.25xx10^(4))/(T) Which statement(s) is (are) correct?

Answer»

(a) The graph plotted `log_(10) K` vs. `1/T` is straight LINE with `E_(a)=24.83 KCAL`
(B) Pre-exponential factor`=13.34`
(c ) The rate constant at `500 K` is `2.35xx10^(-5) sec^(-1)`
(d) `E_(a)=30.63 kcal`

Solution :N//A
46.

Rate constant K = 2.303 "min"^(–1) for a particular reaction the initial concentration of the reactant is 1 mole/litre then rate of reaction after 1 minute is :-

Answer»

2.303 M `"MIN"^(-1)`
0.2303 M `"min"^(-1)`
0.1 M `"min"^(-1)`
None

Solution :`K=2.303/t "LOG" C_o/C_t`
`c_t`=0.1
RATE= `k_1[c_t]`
Rate = 0.2303 M `"min"^(-1)`
47.

Rate constant k for a first order reactions has been found to be 2.54 xx 10^(-3) sec^(-1). Calculate its 3//4^(th) life. (log 4 = 0.6020)

Answer»

SOLUTION :`K = (2.303)/(t) log.(a)/(a-x)`
`k -2.54 xx 10^(-3)sec^(-1), t_(3//4) = ?`
48.

Rast method is based upon the use of …………………..as solvent whose molal depression constant is ……………… .

Answer»

Solution :camphor, `"39.7 K kg MOL"^(-1)`
49.

Rate constant for a reaction is lamda. Average life is representant by

Answer»

`1//LAMDA`
`LN 2//lamda`
`(lamda)/(SQRT2)`
`(0.693)/(lamda)`

ANSWER :D
50.

Rate constant for a reaction is 1.85 xx 10^(2)s^(-1). Give the order of reaction.

Answer»

SOLUTION :FIRST ORDER REACTION.