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(i) The rate constant for a first order reaction is 1.54 times 10^(-3)s^(-1). Calculate its half life time. (ii) Explain about protective action of colloid. |
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Answer» Solution :(i) We know that. `t_(1//2)=0.693//k` `t_(1//2)=0.693//1.54 times 10^(-3)s^(-1)=450s` (ii) 1. Lyophobic sols are PRECIPITATED readily even with small amount of electrolytes. But they are stabilised by the ADDITION of small amount of lyophillic colloid. 2. A small amount of gelatine sol is added to gold sol to protect gold sol. 3. Gold number is a measure of PROTECTING power of a colloid. Gold number is defined asthe number of milligrams of hydrophillic colloid that will just prevent the PRECIPITATION of 10 ml of gold sol on the addition of 1ml of 10% NaCl solution. Smaller the gold number, greater the PROTECTIVE power. |
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