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(a) What are neutral oxides? Explain the nature of zinc oxide with the help of the reactions. (b) Define ‘molar conductivity’ and ‘zero order reaction’. (c) In a first order reaction x → y, 40% of the given sample of compound remains unreacted in 45 minutes. Calculate rate constant of the reaction. |
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Answer» a. 1. Neutral oxides: Oxides which are neither acidic nor basic are called as neutral oxides. eg. CO, NO and N2O 2. ZnO is an amphoteric oxide (show both acidic and basic characterstics). This oxide react with acids as well as bases to form salts. Basic character (Reaction with acid) ZnO(s) (Basic) + 2HCL(eq) → ZnCl2(eq) (Zinc chloride) + H2O(l) Acidic character (Reaction with base) ZnO(eq) (Acidic) + 2NaOH (excess) → Na2ZnO2(eq) + H2O(l) b. 1. Molar conductivity is defined as the conductance of a volume of solution containing 1 mole of dissolved electrolyte when placed between two parallel electrodes 1 cm apart and large enough to contain between them all the solution. 2. Zero order reaction is the reaction whose rate is independent of the reactant concentration and remains constant throughout the course of the reaction. c. Given: For a first order reaction, amount of reactant that remains after 45 minutes = 40% To find: Rate constant (k) Formula : k = \(\frac{2.303}{t}log_{10}\frac{[A]_o}{[A]_t}\) Calculation: [A]0 = 100, [A]t = 40, t = 45 min From formula, k = \(\frac{2.303}{t}log_{10}\frac{[A]_o}{[A]_t}\) ∴ k = \(\frac{2.303}{t}log_{10}\frac{100}{40}\) ∴ k = 0.02036 min–1 |
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