Which metal does not react with cold or hot water,but reacts with steam to produce $H_2$ gas?

An element $A$ burns with a golden yellow flame in air. It reacts with another element $B$ (atomic number $17$) to give a product $C$. An aqueous solution of product $C$ on electrolysis gives a compound $D$ and liberates hydrogen. Identify $A$,$B$,$C$,and $D$. Also,write down the equations for the reactions involved.

Which method,other than the Contact process,is used for the production of sulfuric acid?

$A$ non-metal $A$ is an important constituent of our food and forms two oxides $B$ and $C$. Oxide $B$ is toxic,whereas $C$ causes global warming.
$(a)$ Identify $A$,$B$,and $C$.
$(b)$ To which Group of the Periodic Table does $A$ belong?

Give the steps involved in the extraction of metals of low and medium reactivity from their respective sulphide ores.

Which mixture of two gases,taken in equal proportions in a gas jar,reacts in the presence of sunlight?