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InterviewSolution
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A granulated sample of aircraft alloy `(Al, Mg, Cu)` weighing `8.72 g` was first treated with alkali and then with very dilute `HCl`, leaving a residue. The residue after alkali boiling weighed `2.10 g` and the acid insoluble residue weighed `0.69 g`. What is the composition of the alloy?A. Weight % of `AI = 75.9%`B. Weigth % of `Cu = 7.9%`C. Weight % of `Mg = 16.2%`D. All the above |
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Answer» Correct Answer - D Let `Al,Mg` and Cu be a,b and c g respectively. `2AI + 2NaOH rarr 2NaAIO_(2) +3H_(2)` `Mg +2HCI rarr MgCI_(2) +H_(2)` `Cu +HCI rarr` No reaction i.e., only AI reacts with `NaOH` and then only Mg reacts with `HCI :. a + b +c = 8.72` `b +c = 2.10` (Residue left afte alkali treatment) `c = 0.69` (Residue left after acid treatment) `:. b = 2.1 - 0.69 = 1.41 g` `a = 8.72 - 2.1 = 6.62g` `:. %` of `AI = (6.62)/(8.72) xx 100 = 75.9` `%` of `Mg = (1.41)/(8.72) xx 100 = 16.2` `%` of `Cu = (0.69)/(8.72) xx 100 = 7.9` |
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