Explain double displacement reaction with two examples each.

Write the missing reactants and products and balance the equation.

$\mathrm{NaOH} + \mathrm{\_\_\_\_\_}\to \mathrm{NaCl} + \mathrm{\_\_\_\_\_}$

Write the missing reactants and products and balance the equation.

${\mathrm{KClO}}_3 \stackrel{\mathrm{Heat}}{\to } \mathrm{\_\_\_\_\_} + \mathrm{\_\_\_\_\_}$

Write the missing reactant and product and balance the equation.

$\mathrm{\_\_\_\_\_} + \mathrm{HCl}\to \mathrm{NaCl} +{\mathrm{H}}_2\mathrm{O}+\mathrm{\_\_\_\_\_}$

 How will you obtain magnesium oxide from magnesium and also give balanced equation for the reaction.