Solder is an alloy of lead and tin. It has a:

Which of the following is a compound of hydrogen and oxygen?

Generally,metals are solid in nature. Which one of the following metals is found in liquid state at room temperature?

Which among the following statements is incorrect for magnesium metal?

$(a)$ $A$ substance $X$,an oxide of a metal,is used extensively in the cement industry. This element is found in our bones also. On treatment with water,it forms a solution which turns red litmus blue. Identify $X$ and also write the chemical reaction involved.
$(b)$ Choose a metal from the following metals which reacts only with hot water: Sodium,magnesium,iron. Mention the products formed during the reaction.

What is the chemical formula of oleum?