Question

Which among the following statements is incorrect for magnesium metal?

• A. It burns in oxygen with a dazzling white flame
• B. It reacts with cold water to form magnesium oxide and evolves hydrogen gas
• C. It reacts with hot water to form magnesium hydroxide and evolves hydrogen gas
• D. It reacts with steam to form magnesium hydroxide and evolves hydrogen gas

Answer 1

The correct option is B

It reacts with cold water to form magnesium oxide and evolves hydrogen gas

Explanation for correct option

(B) It reacts with cold water to form magnesium oxide and evolves hydrogen gas

Magnesium

• Magnesium is a chemical element with the symbol $\mathrm{Mg}$.
• $\mathrm{Mg}$ has an atomic number of $12$.
• It is a solid that has a lustrous grey color and many of the same physical and chemical characteristics as the other five alkaline earth metals.

Magnesium reacts with cold water

• Magnesium metal does not react with cold water.
• Magnesium hydroxide is insoluble, preventing water from coming into contact with the metal.

Explanation for incorrect options

(A) It burns in oxygen with a dazzling white flame

• Magnesium metal burns with oxygen $\left({\mathrm{O}}_2\right)$ to form Magnesium Oxide $\left(\mathrm{MgO}\right)$, which produces a dazzling white flame.
• The reaction is as follows:

$2\mathrm{Mg}\left(\mathrm{s}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\to 2\mathrm{MgO}\left(\mathrm{s}\right)+\mathrm{Energy}$

(C) It reacts with hot water to form magnesium hydroxide and evolves hydrogen gas

• Magnesium metal reacts with hot water $\left({\mathrm{H}}_2\mathrm{O}\right)$ to form Magnesium hydroxide $\left(\mathrm{Mg}{\left(\mathrm{OH}\right)}_2\right)$ and hydrogen $\left({\mathrm{H}}_2\right)$ gas.
• The reaction is as follows:

$\mathrm{Mg}\left(\mathrm{s}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to \mathrm{Mg}{\left(\mathrm{OH}\right)}_2\left(\mathrm{aq}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right)$

(D) It reacts with steam to form magnesium hydroxide and evolves hydrogen gas

• Magnesium metal reacts with steam $\left({\mathrm{H}}_2\mathrm{O}\right)$ to form Magnesium hydroxide $\left(\mathrm{Mg}{\left(\mathrm{OH}\right)}_2\right)$ and hydrogen $\left({\mathrm{H}}_2\right)$ gas.
• The reaction is as follows:

$\mathrm{Mg}\left(\mathrm{s}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)\to \mathrm{Mg}{\left(\mathrm{OH}\right)}_2\left(\mathrm{aq}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right)$

Therefore, the correct option is (B) It reacts with cold water to form magnesium oxide and evolves hydrogen gas.