Question

1) The decomposition of N2O5(g) is a first-order reaction. If the initial concentration of N2O5 (g) is 0.03 mol/L, what will be its concentration after 30 min, if the rate constant of the reaction is 1.35 × 10–4 s–1.

2) What will be the initial rate of a reaction if its rate constant is 10–3 min–1 and the concentration of the reactant is 0.2 mol dm–3? How much of the reactant will be converted into the products in 200 min?

3) The rate constant for a first-order reaction N2 + O5 → 2NO2 + 1/2 O2 is 6.2 × 10–6 s–1. If the initial concentration of N2O5 is 15 mol L–1, calculate the initial rate of the reaction.

4) To measure the rate of decomposition of hydrogen peroxide at a particular temperature its solution is titrated with acidic KMnO4 solution. The results obtained are as follows:

Time t (min) 0 10 20

Vol of KMnO4 used 22.8 13.8 8.3

Show that the reaction is of first order and calculate the rate constant.

5) A reaction is first order with respect to reactant X. It has a rate constant of 8 min–1. If the

initial concentration of [X] = 7.0 mol L–1, find the time required by [X] to reach the value of

0.07 mol L–1.

6) The following data were obtained on the hydrolysis of methyl acetate at 25 °C in 0.35 N

hydrochloric acid. Establish that the reaction follows first-order kinetics. Calculate the rate

constant.

t (s) 0 4500 7140 ∞

mL of alkali used 24.36 29.32 31.72 47.15

7) The optical rotation of sucrose in 0.9 M HCl at different time intervals is given in the

following table. Show that the reaction is of first order. Calculate the rate constant.

Time (min) 0 6.18 18.00 27.05 ∞

Rotation (degrees) +24.09 +21.4 +17.7 +15.0 −10.74

8) The following results were obtained in the decomposition of N2O4 in CCl4

at 44 °C:

t (s) 1200 1800 2400 ∞

x (mL) 11.40 15.53 1 18.90 34.75

where x denotes the volume of oxygen evolved in t seconds. Show that the reaction is of first order.

9) Ethyl acetate was hydrolysed by NaOH. Equal concentration of NaOH and ethyl acetate was

used for the hydrolysis reaction. 25 mL of the reaction mixture was titrated against standard

acid at regular time intervals. From the data given below, establish that it is a second-order

reaction:

t (min) 0 5 15 25 35

mL of acid used 16.00 10.24 6.13 4.32 3.41

10) Ethyl nitro benzoate was hydrolysed by aqueous sodium hydroxide at 25 °C. The progress of

the reaction was followed by titrating the hydroxide against standard acid at different intervals of time. From the data given below, show that the reaction is of second order.

t (min) 0 95 140 222 334 805 1384

mL of acid used 10 9.3 9.0 8.5 7.9 6.1 4.8

11) The decomposition of a substance follows first-order kinetics. Calculate the rate constant of

the reaction if its half-life is 35 min.

12) For a first-order reaction, prove that the time taken for three fourth completion of the reaction is double the time taken for half completion of the reaction, that is, t3/4 / t1/2 = 2. If the rate constant k for a first-order reaction is 5.48 × 10–14 s–1, find the time taken for two third of the reaction to be completed.

13) Decomposition of nitramide follows first-order kinetics. Its half-life is 3.2 h at 15 °C.

NH2 NO2 (aq) → N2O (g) +H2O (l)

If 7.1 g of NH2 NO2 decomposes, calculate the time taken for 90% NH2NO2 to decompose.

14) Find the activation energy of the reaction if the first-order rate constant becomes eight times on increasing the temperature from 300 to 450 K. (Gas constant R= 8.314 J K–1 mol–1)

15) The half-life of a first-order reaction is 30 min at 27 °C and 10 min at 47 °C. Determine the

activation energy of the reaction

16) The first-order decomposition of N2O4 into NO2 has a k value of 4.5 × 103 s–1 at 1 °C

and an energy of activation of 58 kJ mol–1. At what temperature its half-life would be 6.93 × 10–5 s.

17) The rate constants of a reaction at 500K and 700K are 0.02 /s and 0.07 /s respectively. Calculate the values of Ea and A.

18) A second order reaction, whose rate constant at 800 oC was found to be 5.0x10-3 l mol-1 s-1 has an activation energy of 45 kJ mol-1. What is the value of the of the rate constant at 875 oC?

19) For a second order reaction one hour is needed for a change off concn. A to a/2. What will be the time for change from a/2 to a/4?

20) What is the special characteristic of a zero order reaction?

Answer 1

Answer:

Unlike the other orders of reaction, a zero-order reaction has a rate that is independent of the concentration of the reactant(s). As such, increasing or decreasing the concentration of the reacting species will not speed up or slow down the reaction rate 20 number answer

Answer 2

Answer:

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