Question

Dry hydrogen when passed over heated metals like $Na$, $K$ and $Ca$, reacts to give their corresponding ______

Answer 1

We need to understand the reaction that takes place between dry hydrogen and metals like $Na$, $K$ and $Ca$. Dry hydrogen is one of the most effective agents in the furnace for reducing the oxides of many metals. When an oxidised metal is heated to a high enough temperature in dry hydrogen, the oxide is reduced to the native metal, and the oxygen emissions mix with the hydrogen to produce water.

Complete answer:
We have to remember that the dry hydrogen when passed over heated metals like $Na$, $K$ and $Ca$, reacts to give their corresponding hydrides. At $350^\circ C$, pure dry hydrogen reacts with sodium to produce sodium hydride. It reacts violently with water to produce sodium hydroxide and hydrogen, with halogens to produce the halide and suitable hydrogen halide, and with oxygen to produce the halide and suitable hydrogen halide, and it burns spontaneously at $230^\circ C$. Similarly it reacts with $K$ and $Ca$ to produce their hydrides.

Note:
It must be noted that when materials develop oxides at low dew points, dry hydrogen atmospheres are employed instead of wet hydrogen. Dry Hydrogen is used to process Molybdenum, Tungsten, and Stainless Steel. Because stainless steel has a high chromium content and readily forms chromium oxide on its surface when heated, it is frequently brazed in a Dry Hydrogen atmosphere. Covalent hydrides are formed when non-metals react with hydrogen. Sulphur, for example, reacts with hydrogen to generate hydrogen sulphide. Dry hydrogen is one of the most effective agents in the furnace for reducing the oxides of many metals.