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Chemical Kinetics — Chemistry STD 12 Science — Question

Bihar BoardEnglish MediumSTD 12 ScienceChemistryChemical Kinetics3 Marks
Question
Nitrogen pentoxide decomposes according to equation: $\text{2N}_{2}\text{O}_{5}\text{(g)}\rightarrow\text{4NO}_{2}\text{(g)}+\text{O}_{2}\text{(g)}.$
This first order reactionwas allowed to proceed at 40° C and the data below were collected:
[N2O5](M) Time (min)
0.400 0.00
0.289 20.0
0.209 40.0
0.151 60.0
0.109 80.0
  1. Calculate the rate constant. Include units with your answer.
  2. What will be the concentration of N2O5 after 100 minutes?
  3. Calculate the initial rate of reaction.
✓

Answer

  1. $\text{k}=\frac{2.303}{t}\log\frac{[A_{o}]}{[A]}$

$\text{k}=\frac{2.303}{\text{20 min}}\log\frac{0.400}{0.289}$

$\text{k} = 0.0163\text{ min}^{–1}$

  1. $\text{k}=\frac{2.303}{\text{t}}\log\frac{[A_o]}{[A]}$

$\text{0.0163}=\frac{2.303}{\text{100}}\log\frac{0.400}{[A]}$

$[\text{A}] = 0.078\text{M}$

  1. $\text{Initial rate R = k}[\text{N}_2\text{O}_5]$

$= 0.0163\text{ min}^{–1} \times (0.400\text{ M})$

$= 0.00652\text{M min}^{–1}.$

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