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15240672380's Question
Chemistry
Posted 7 months ago

6) At 500C500^{\circ} \mathrm{C}, cyclopropane (C3H6)\left(\mathrm{C}_{3} \mathrm{H}_{6}\right) rearranges to propene (CH3CH=CH2)\left(\mathrm{CH}_{3}-\mathrm{CH}=\mathrm{CH}_{2}\right). The reaction is 1st order with a rate constant k=6.7×104 s1k=6.7 \times 10^{-4} \mathrm{~s}^{-1}.
a. Write the rate equation, and determine the rate of reaction when the conversion xx is 0 and 0.5 , given that the initial concentration of
[3.35×105 molI1 s1;1.675×105 molI1 s1]
\left[3.35 \times 10-5 \mathrm{~mol} \mathrm{I}^{-1} \mathrm{~s}^{-1} ; 1.675 \times 10^{-5} \mathrm{~mol} \mathrm{I}^{-1} \mathrm{~s}^{-1}\right]

b. Integrate the rate equation and determine:
i. The concentration of cyclopropane after 30 minutes
[0.015M]
[0.015 \mathrm{M}]

ii. The time taken for the concentration of cyclopropane to fall to 0.001 mol2litr10.001 \mathrm{~mol}^{2} \mathrm{litr}^{-1}.
[5839 s,(97 minutes)] 
[5839 \mathrm{~s},(97 \text { minutes)] }

iii. The fractional conversion of cyclopropane and the concentration of propene after 50 minutes.
[0.866; 0.0433M]0.0433 \mathrm{M}]
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Answer from Sia
Posted 7 months ago
Solution
1
Write the rate equation: For a first-order reaction, the rate equation is given by the formula rate=k[A]rate = k[A], where kk is the rate constant and [A][A] is the concentration of the reactant
2
Determine the rate of reaction at conversion $x = 0$: When x=0x = 0, the concentration of cyclopropane is at its initial value. The rate of reaction is then rate=k[A]0=(6.7×104 s1)([A]0)rate = k[A]_0 = (6.7 \times 10^{-4} \text{ s}^{-1})([A]_0)
3
Determine the rate of reaction at conversion $x = 0.5$: When x=0.5x = 0.5, the concentration of cyclopropane is half of its initial value. The rate of reaction is then rate=k[A]0.5=(6.7×104 s1)([A]02)rate = k[A]_{0.5} = (6.7 \times 10^{-4} \text{ s}^{-1})(\frac{[A]_0}{2})
4
Integrate the rate equation to find concentration after 30 minutes: The integrated rate equation for a first-order reaction is ln([A]0/[A])=kt\ln([A]_0/[A]) = kt. Solving for [A][A] after 30 minutes (1800 seconds) gives the concentration of cyclopropane
5
Determine the time for concentration to fall to $0.001 \text{ M}$: Using the integrated rate equation, solve for tt when [A]=0.001 M[A] = 0.001 \text{ M}
6
Calculate the fractional conversion and concentration of propene after 50 minutes: The fractional conversion is given by x=1[A]/[A]0x = 1 - [A]/[A]_0. The concentration of propene is equal to the initial concentration of cyclopropane minus its concentration after 50 minutes
1 Answer
The rate of reaction at conversion x=0x = 0 is 3.35×105 mol L1s13.35 \times 10^{-5} \text{ mol L}^{-1}\text{s}^{-1} and at conversion x=0.5x = 0.5 is 1.675×105 mol L1s11.675 \times 10^{-5} \text{ mol L}^{-1}\text{s}^{-1}.
2 Answer
The concentration of cyclopropane after 30 minutes is 0.015 M0.015 \text{ M}.
3 Answer
The time taken for the concentration of cyclopropane to fall to 0.001 M0.001 \text{ M} is 5839 seconds (97 minutes).
4 Answer
The fractional conversion of cyclopropane after 50 minutes is 0.866, and the concentration of propene is 0.0433 M0.0433 \text{ M}.
Key Concept
The rate equation for a first-order reaction relates the rate of reaction to the concentration of the reactant and the rate constant.
Explanation
The rate of a first-order reaction decreases as the concentration of the reactant decreases, which is reflected in the rate of reaction at different conversion levels.

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