4.1 From the rate expression for the following reactions, determine their order of reaction and the dimensions of the rate constants.
(i) 3NO(g) → N2O(g) ; Rate = k[NO]2
(ii) H2O2 (aq) + 3I– (aq) + 2H+ → \(I_{3}^{-}\) + 2H2O(l) ; Rate = k[H2O2][I-]
(iii) CH3CHO (g) → CH4 (g) + CO(g) ; Rate = k[CH3CHO]3/2
(iv) C2H5Cl (g) → C2H4 (g) + HCl(g) ; Rate = k[C2H5Cl]
(i)
Step 1:
Given,
Rate = k[NO]
Therefore, the order of the reaction = 2
Step 2:
Calculate the dimensions of the rate constants as follows:
\(
k=\frac{\text { Rate }}{[N O]^{2}} \\
\begin{aligned}
=\frac{mol L^{-1} s^{-1}}{\left(mol L^{-1}\right)^{2}} \\
=\frac{m o l L^{-1} s^{-1}}{m o l^{2} L^{-2}} \\
=mol^{-1}Ls^{-1}
\end{aligned}\)
(ii) Given,
rate = k[H2O2][I-]
Therefore, order of the reaction = 2
Calculate the dimensions of the rate constants as follows:
\(
k=\frac{\text { Rate }}{[H_{2}O^{2}][I^{-}]} \\
\begin{aligned}
=\frac{mol L^{-1} s^{-1}}{\left(mol L^{-1}\right)^{2}} \\
=\frac{m o l L^{-1} s^{-1}}{m o l^{2} L^{-2}} \\
=mol^{-1}Ls^{-1}
\end{aligned}\)
(iii)
Step 1:
Given,
rate = k[CHCHO]
Therefore, order of the reaction = \(\frac{3}{2}\)
Step 2:
(iv) Given rate = K Therefore, order of the reaction =1
Dimension of
=
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