Which one of the following statements is not correct? from Chem

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 Multiple Choice QuestionsMultiple Choice Questions

291.

For the reaction, N2 + 3H2 → 2NH3, If straight d fraction numerator left square bracket NH subscript 3 right square bracket over denominator dt end fraction space equals space 2 space straight x space 10 to the power of negative 4 end exponent space mol space straight L to the power of negative 1 end exponent straight s to the power of negative 1 comma end exponent the value of negative fraction numerator straight d left square bracket straight H subscript 2 right square bracket over denominator dt end fraction would be

  • 3 x 10-4 mol L-1 s-1

  • 4 x 10-4 mol L-1s-1

  •  6 x 10-4 mol L-1s-1

  •  6 x 10-4 mol L-1s-1

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292.

In the reaction,

BrO to the power of minus subscript 3 space left parenthesis aq right parenthesis space plus space 5 Br to the power of minus space left parenthesis aq right parenthesis space plus 6 straight H to the power of plus space rightwards arrow space 3 Br subscript 2 left parenthesis straight l right parenthesis space plus 3 straight H subscript 2 straight O space left parenthesis straight l right parenthesis
The rate of appearance of bromine (Br)2 is related to rate of disappearnace of bromide ions as following

  • fraction numerator straight d left square bracket Br subscript 2 right square bracket over denominator dt end fraction space equals space minus 3 over 5 fraction numerator straight d left square bracket Br to the power of minus right square bracket over denominator dt end fraction space
  • fraction numerator straight d left square bracket Br subscript 2 right square bracket over denominator dt end fraction space equals space minus space 5 over 3 fraction numerator d left square bracket B r right square bracket over denominator d t end fraction
  • fraction numerator straight d left square bracket Br subscript 2 right square bracket over denominator dt end fraction space equals space 5 over 3 fraction numerator straight d left square bracket Br to the power of minus right square bracket over denominator dt end fraction
  • fraction numerator straight d left square bracket Br subscript 2 right square bracket over denominator dt end fraction space equals space 5 over 3 fraction numerator straight d left square bracket Br to the power of minus right square bracket over denominator dt end fraction
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293.

The rate constant k1 and k2 for two different reactions are 1016. e-2000/T and 1015.e-1000/T respectively. The temperature at which k1 = k2

  • 1000 K 

  • 2000/2.303 K 

  • 2000 K 

  • 2000 K 

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294.

The bromination of acetone cytosine and guanine solution is represented by this equation.
 CH3COCH3 (aq) + Br2 (aq) →CH3COCH2Br (aq) + H+ (aq) + Br- (aq)
These kinetic data were obtained for given reaction concentrations.

Initial Concentrations, M
[CH3COOH] [Br2] [H+]
0.30 0.05 0.05
0.30 0.10 0.05
0.30 0.10 0.10
0.40 0.05 0.20

Initial rate, disappearance of Br2, ms-1
                   5.7 x 10-5
                   5.7 x 10-5
                   1.2 x 10-4
                   3.1 x  10-4
Based on these data, the rate equation is
  • Rate = k[CH3COCH3][H+]

  • Rate = k[CH=COCH3][Br2]

  • Rate = k [CH3COCH3][Br2][H+]

  • Rate = k [CH3COCH3][Br2][H+]

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295.

The reaction of hydrogen and iodine monochloride is given as:
H2 (g) + 2ICl (g) → 2 HCl (g)  + I2 (g)
This reaction is of first order with respect to H2 (g) and ICI (g), following mechanisms were proposed:

Mechanism A:
H2 (g) + 2 ICl (g)  → 2 HCl (g) + I2 (g) 

Mechanism B:
H2 (g) + ICl (g) →HCl (g) + HI (g) ;slow
HI (g) + ICl (g)  → HCl (g) + I2 (g); fast

Which of the above mechanism (s) can be consistent with the given information about the reaction? 

  • B only

  • A and B both

  • Neither A nor B

  • Neither A nor B


296.

In a first order reaction A →B, if k israte constant and initial concentration of the reactant A is 0.5 A M then the half -life is : 

  • 0.693/0.5 k

  • log2/k

  • log space 2 space divided by space straight k square root of 0.5 end root
  • log space 2 space divided by space straight k square root of 0.5 end root

297.

If 60% of a first order reaction was completed in 60 min, 50% of the same reaction would be completed in approximately:

  • 50 min

  • 45 min

  • 60 min

  • 60 min


298.

For the reaction 

2A + B → 3C + D

Which of the following does not express the reaction rate?

  • fraction numerator straight d left square bracket straight C right square bracket over denominator 3 dt end fraction
  • negative fraction numerator straight d left square bracket straight B right square bracket over denominator dt end fraction
  • fraction numerator straight d left square bracket straight D right square bracket over denominator dt end fraction
  • fraction numerator straight d left square bracket straight D right square bracket over denominator dt end fraction
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299.

Consider the reaction

N2 (g) + 3 H2 (g) → 2 NH3 (g) 

The equality relationship between fraction numerator straight d left square bracket NH subscript 3 right square bracket over denominator dt end fraction space and space fraction numerator negative straight d left square bracket straight H subscript 2 right square bracket over denominator dt end fraction is:

  • fraction numerator straight d left square bracket NH subscript 3 right square bracket over denominator dt end fraction space equals space minus space 1 third fraction numerator straight d left square bracket straight H subscript 2 right square bracket over denominator dt end fraction
  • fraction numerator straight d left square bracket NH subscript 3 right square bracket over denominator dt end fraction space equals space minus space 2 over 3 fraction numerator straight d left square bracket straight H subscript 2 right square bracket over denominator dt end fraction
  • plus fraction numerator straight d left square bracket NH subscript 3 right square bracket over denominator dt end fraction space equals space minus 3 over 2 fraction numerator straight d left square bracket straight H subscript 2 right square bracket over denominator dt end fraction
  • plus fraction numerator straight d left square bracket NH subscript 3 right square bracket over denominator dt end fraction space equals space minus 3 over 2 fraction numerator straight d left square bracket straight H subscript 2 right square bracket over denominator dt end fraction
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300.

Which one of the following statements is not correct?

  • Catalyst does not initiate any reaction

  • The value of equilibrium constant is changed in the presence of a catalyst in the reaction at equilibrium

  • Enzymes catalyse mainly bio-chemical reactions

  • Enzymes catalyse mainly bio-chemical reactions


B.

The value of equilibrium constant is changed in the presence of a catalyst in the reaction at equilibrium

A catalyst decreases activation energies of both the forward and backward reaction by the same amount, therefore, it speeds up both forward and backward reaction by the same rate. The equilibrium constant is therefore not affected by the catalyst at a given temperature.

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