Question

a) Name the salt formed by the reaction between magnesium hydroxide [ $Mg(O{H}_2)$ ] and dil. hydrochloric acid ( $HCl$ ).
b) Write the equation for the reaction.
c) Which is the acid required for the preparation of magnesium sulphate?

Answer 1

Hint: Magnesium hydroxide is regarded as a base and hydrochloric acid as an acid by the Arrhenius theory. So, the reaction will be a neutralization reaction. Based on this you can determine the salt formed. Now write the equation for the reaction taking place. Determine the ions of the compound magnesium sulfate. Based on this you can determine the parent acid involved in the neutralization reaction.

Complete step-by-step answer:
a) The reaction between magnesium hydroxide and hydrochloric acid is an example of neutralisation reaction. The hydroxide and hydrogen ions will combine to form water. The remaining ions combine to produce the salt of neutralisation. The salt is magnesium chloride. The chemical formula for the compound is $MgC{l}_2$.
b) The equation for the neutralisation reaction is given below:
$$Mg{(OH)}_2+2HCl\to MgC{l}_2+2H_{2}O$$
c) Magnesium sulphate has magnesium ions and sulphate ions when dissolved in water. Magnesium ions will be from the base and sulphate will be from the parent acid. Thus, the parent acid for the formation of magnesium sulphate is sulfuric acid. The chemical formula for the compound is $H_{2}S{O}_4$.

Note: In the equation of neutralisation we observe that 2 moles of water are formed for every mole of base. This is because magnesium hydroxide provides two hydroxide ions per molecule. On the other hand, hydrochloric acid can release only 1 hydrogen ion per molecule.