Question

mg(oh)₂ + hcl → mgcl₂ + h₂o
al(oh)₃ + h₂so₄ → al₂(so₄)₃ + h₂o

Explanation:

Step1: Balance the Mg atoms

On the left, we have 1 Mg in $\ce{Mg(OH)2}$, and on the right, 1 Mg in $\ce{MgCl2}$. So Mg is balanced.

Step2: Balance the Cl atoms

On the right, we have 2 Cl in $\ce{MgCl2}$. So we need 2 HCl on the left. Now the equation is $\ce{Mg(OH)2 + 2HCl -> MgCl2 + H2O}$.

Step3: Balance the H and O atoms

On the left, we have 2 O from $\ce{Mg(OH)2}$ and 2 H from 2 HCl (total H: 2 from HCl + 2 from $\ce{Mg(OH)2}$ = 4? Wait, no: $\ce{Mg(OH)2}$ has 2 H (from 2 OH⁻) and 2 HCl has 2 H. So total H on left: 2 + 2 = 4. On the right, $\ce{H2O}$ has 2 H per molecule. So we need 2 $\ce{H2O}$ to balance H (2×2 = 4 H). Let's check O: left has 2 O (from $\ce{Mg(OH)2}$), right has 2 O (from 2 $\ce{H2O}$). Perfect. So the balanced equation is $\ce{Mg(OH)2 + 2HCl -> MgCl2 + 2H2O}$.

Answer:

The balanced chemical equation is $\boldsymbol{\ce{Mg(OH)2 + 2HCl -> MgCl2 + 2H2O}}$