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191. The decomposition of a compound is found to follow a first-order rate law. If it takes 15 minutes for 20 percent of original material to react.
Calculate :

(i) the specific rate constant
(ii) the time at which 10 percent of the original material remains unreacted
(iii) the time it takes for the next 20 percent of the reactant left to react after the first 15 minutes.

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192. Rate constant k of a reaction varies with temperature according to the equation:

log k constant

- \frac{E_{a}}{2.303} \frac{1}{T}

where E_a is the energy of activation for the reaction. When a graph is plotted for log k versus 1/T a straight line with a slope - 6670 k is obtained. Calculate energy of activation for this reaction. State the units (R = 8.314 J K^–1 mol^–1)

472 Views

Long Answer Type

193.

The reaction:
SO₂ + Cl₂ SO₂ + Cl₂is a first order reaction with k₁ = 2.2 x 10^–5 s^–1 at 575 K. What percentage of a initial amount of SO₂ Cl₂will get decomposed in 90 minutes when the reaction is carried out at 575 K?

125 Views

194.

The reaction
SO₂Cl₂ → SO₂ + Cl₂is a first order reaction with k = 2.2 x 10^–5s^–1 at 320° C. Calculate the percentage of SO₂Cl₂ that is decomposed on heating this gas for 30 minutes.

980 Views

Short Answer Type

195. A first order reaction takes 69.3 minutes for 50% completion. Set up an equation determining the time needed for 80% completion of the reaction.

932 Views

Long Answer Type

196. The activation energy of a reaction is 75.2 kJ mol^–1 in the absence of a catalyst and 50.14 kJ mol^–1 with a catalyst. How many times will the rate of reaction grow in the presence of the catalyst if the reaction proceeds at 25°C?
(R = 8.314 J K^–1 mol^–1)

782 Views

Short Answer Type

197. The rate of a particular reaction doubles when temperature changes from 27°C to 37°C. Calculate the activation energy of such reaction.

According to the Arrhenius equation

\log \frac{k_{2}}{k_{1}} = \frac{Ea}{2.303 R} (\frac{T_{2} - T_{1}}{T_{1} T_{2}}) \log \frac{1}{2} = \frac{Ea}{2.303 \times 8.314} \times (\frac{310 - 300}{310 \times 300}) Ea = \frac{19.147 \times 93000 \times 0.3010}{10} = \frac{19.147 \times 9300 \times 0.3010}{1000} Ea = 52.99 kJ {mol}^{- 1} .

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198. Thermal decomposition of a compound is of first order. If 50% of a sample of the compound is decomposed in 120 minutes, how long will it take for 90% of the compound to decompose.

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199. In the Arrhenius equation for a certain reaction, the value of A and Ea (activation energy) are 4 x 10¹³ sec^–1 and 98.6 mol^–1 respectively, If the reaction is of first order, at what temperature will its half life period be the minutes?

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200. The pressure of a gas decomposing at the surface of a solid catalyst has been measured at different times and the results are given below:

t/s	0	100	200	300
p/pascal	4.0 x 10³	3.5 x 10³	3.0 x 10³	2.5 x 10³

Determine the order of reaction, its rate constant and half-life period.

121 Views