Question

Magnesium reacts with steam to form___ and ___.

Answer 1

Hint: Generally metal reacts with water to give metal hydroxide and hydrogen gas. But as when metal reacts with hot water; metal hydroxide thermally decomposes to give metal oxide and water.

Complete answer:
Magnesium is an element of group 2 and period 3. It belongs to alkaline earth metal. The electronic configuration of magnesium is $$1{\text{s}}^{2}2{\text{s}}^{2}2{\text{p}}^{6}3{\text{s}}^2$$ .
Magnesium burns in steam to produce white magnesium oxide and hydrogen gas. The reaction is as follow as: $$\text{M}{\text{g}}_{\left(\text{s}\right)}+{\text{H}}_2{\text{O}}_{\left(\text{s}\right)}\to \text{Mg}{\text{O}}_{\left(\text{s}\right)}+{\text{H}}_{2\left(\text{g}\right)}$$ . Very clean magnesium ribbon has a very slight reaction with cold water. After several minutes, some bubbles of hydrogen form on its surface, and the coil of magnesium ribbon usually float to the surface. However, the reaction soon stops because the magnesium hydroxide formed is almost insoluble in water and forms a barrier on the magnesium preventing further reaction. This is as follow as: $$\text{M}{\text{g}}_{\left(\text{s}\right)}+2{\text{H}}_2{\text{O}}_{\left(\text{l}\right)}\to \text{Mg}{\left(\text{OH}\right)}_{2\left(\text{s}\right)}+{\text{H}}_{2\left(\text{g}\right)}$$ .
Other elements of alkaline earth metal on reaction with water, metal reacts slowly with water to give hydrogen and metal hydroxide. Beryllium of alkaline earth metal does not react with water. Magnesium reacts only with hot water and does not react with cold water. Calcium, Strontium and Barium react with cold water but not as energetically as alkali metals. Order of reactivity of alkaline earth metal with water is: $$\text{Ba}>\text{Sr}>\text{Ca}>\text{Mg}>\text{Be}$$ .

Thus, the correct answer is Magnesium reacts with steam to form magnesium oxide and hydrogen gas.

Note:
As a general rule, if a metal reacts with cold water, we get the metal hydroxide. If it reacts with steam, the metal oxide is formed. This is because the metal hydroxide thermally decomposes or we can say split up on heating to give the oxide and water.