Question 10 of 37intermediate🔧 ApplyShort Answer3 marks

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)3\text{NO}(g) \rightarrow \text{N}_2\text{O}(g) Rate =k[NO]2= k[\text{NO}]^2 (ii) H2O2(aq)+3I−(aq)+2H+→2H2O(l)+I3−\text{H}_2\text{O}_2(\text{aq}) + 3\text{I}^-(\text{aq}) + 2\text{H}^+ \rightarrow 2\text{H}_2\text{O}(\text{l}) + \text{I}_3^- Rate =k[H2O2][I−]= k[\text{H}_2\text{O}_2][\text{I}^-] (iii) CH3CHO(g)→CH4(g)+CO(g)\text{CH}_3\text{CHO}(\text{g}) \rightarrow \text{CH}_4(\text{g}) + \text{CO}(\text{g}) Rate =k[CH3CHO]3/2= k[\text{CH}_3\text{CHO}]^{3/2} (iv) C2H5Cl(g)→C2H4(g)+HCl(g)\text{C}_2\text{H}_5\text{Cl}(\text{g}) \rightarrow \text{C}_2\text{H}_4(\text{g}) + \text{HCl}(\text{g}) Rate =k[C2H5Cl]= k[\text{C}_2\text{H}_5\text{Cl}]

(i)
Answer

Order of reaction = 2; Dimensions of rate constant (k) = mol⁻¹ L s⁻¹

(ii)
Answer

Order of reaction = 2; Dimensions of rate constant (k) = mol⁻¹ L s⁻¹

(iii)
Answer

Order of reaction = 3/2; Dimensions of rate constant (k) = mol⁻¹/² L¹/² s⁻¹

(iv)
Answer

Order of reaction = 1; Dimensions of rate constant (k) = s⁻¹

Explanation

The order of reaction is determined by summing the exponents of concentration terms in the rate expression. For dimensions of rate constant, use the formula: k = Rate/[concentration]^n = (concentration/time) × 1/(concentration)^n, where n is the order. Using SI units (mol L⁻¹ for concentration and s for time), the dimensions can be derived. For zero order: mol L⁻¹ s⁻¹; first order: s⁻¹; second order: mol⁻¹ L s⁻¹. For fractional orders like 3/2, substitute n = 3/2 in the formula.

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