You are provided with two containers made up of copper and aluminium. You are also provided with solutions of dilute HCl, dilute HNO3, ZnCl2 and H2O. In which of the above containers these solutions can be kept? 8 E XEMPLAR P ROBLEMS – SCIENCE
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(A) When solutions are kept in copper container (a) Dilute HCl Copper does not react with dilute HCl. Therefore, it can be kept. (b) Dilute HNO3 Nitric acid acts as a strong oxidising agent and reacts with copper vessel, therefore cannot be kept. (c) ZnCl2 Zinc is more reactive than copper (Cu) therefore, no displacement reaction occurs and hence can be kept. (d) H2O Copper does not react with water. Therefore, can be kept. (B) When solutions are kept in aluminium containers (a) Dilute HCl Aluminium reacts with dilute HCl to form its salt and hydrogen is evolved. Therefore, cannot be kept. 2 Al + 6HCl → 2 AlCl3 + 3 H2 (b) Dilute HNO3 Aluminium gets oxidised by dilute HNO3 to form a layer of Al2O3 and can be kept. (c) ZnCl2 Aluminium being more reactive than zinc can displace zinc ion from the solution. Therefore, the solution cannot be kept. 2 Al + 3 ZnCl2 → 2 AlCl3 + 3Zn (d) H2O Aluminium does not react with cold or hot water. Therefore, water can be kept. Aluminium is attacked by steam to form aluminium oxide and hydrogen 2Al (s) + 3H2O (g) → Al2O3 (s) + 3H2 (g) 122 E XEMPLAR P ROBLEMS – SCIENCE %*#26'4 ANSWERS /WNVKRNG%JQKEG3WGUVKQPU