Question

Three metal samples of magnesium, aluminium and iron were taken and rubbed with sand paper. These samples were then put separately in test tubes containing dilute hydrochloric acid. Thermometers were also suspended in each test tube so that their bulbs dipped in the acid. The rate of formation of bubbles was observed. The above activity was repeated with dilute nitric acid and the observations were recorded. Answer the following questions :

Assertion (A) : A piece of Zinc metal gets reddish brown coating when kept in copper sulphate solution for some time. Reason (R) : Copper is more reactive metal than Zinc.

Sodium metal is stored under kerosene oil. Why ?

Some metal oxides are soluble in water. What are the aqueous solutions of these oxides called ? Write one example of such a solution.