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Standard XII

Chemistry

Assigning Oxidation Numbers

Activation en...

Question

Activation energy for the acid catalysed hydrolysis of sucrose is $6.22 k J m o l^{- 1}$ , while the activation energy is only $2.15 k J m o l^{- 1}$ when hydrolysis is catalysed by the enzyme sucrase. Explain.

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Solution

In the hydrolysis of sucrose, the enzyme sucrase reduces the activation energy from $6.22 k J m o l^{- 1}$ to $2.15 k J m o l^{- 1}$ .

This is because enzymes, the biocatalysts, reduce the magnitude of activation energy by providing an alternative path.

Actually, active site of the enzyme holds the substrate molecule in a suitable position by lock and key mechanism and by this the substrate is better positioned to be attacked by the reagent effectively.

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Similar questions

Activation energy for the acid catalysed hydrolysis of sucrose is 6.22 KJ $m o l^{-}$ , while the activation energy is only 2.15 KJ $m o l^{-}$ when hydrolysis is catalysed by the enzyme sucrase. Explain.

Q. Calculate the ratio of the catalysed and uncatalysed rate constant at

20^{o} C

if the energy of activation of a catalysed reaction is

20

k J

{m o l}^{- 1}

and for the uncatalysed reaction is

75

k J

{m o l}^{- 1}

Q. The rate constant is given by Arrhenius equation,

k = A e^{- E_{a} / R T}

Calculate the value of

l o g_{10} \frac{k_{c a}}{k_{u n}}

27^{\circ} C

.
where,

k_{c a}

and

k_{u n}

are the rate constants for catalysed and uncatalysed reaction respectively.
The energy of activation of catalysed and uncatalysed reactions are

162 k J m o l^{- 1}

and

350 k J m o l^{- 1}

respectively.

Q. An enzyme ‘catalase’ increases the rate of decomposition of

H_{2} O_{2} (a q)

into

H_{2} O (l)

and

O_{2} (g)

e^{40}

times at

300 K

. The activation energy of enzyme catalysed reaction is

4.0 k c a l / m o l

. The activation energy of uncatalysed reaction is

Q. The following data were obtained for a given reaction at

300 K

Reaction	Energy of activation $(k J {m o l}^{- 1})$
Uncatalysed	$76$
Catalysed	$57$

The factor by which rate of catalysed reaction is increased, is:

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Assigning Oxidation Numbers

Standard XII Chemistry

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Activation energy for the acid catalysed hydrolysis of sucrose is 6.22 kJ mol−1, while the activation energy is only 2.15 kJ mol−1 when hydrolysis is catalysed by the enzyme sucrase. Explain.

Activation energy for the acid catalysed hydrolysis of sucrose is $6.22 k J m o l^{- 1}$ , while the activation energy is only $2.15 k J m o l^{- 1}$ when hydrolysis is catalysed by the enzyme sucrase. Explain.