Write balanced equations for the reactions of LiOH and NaOH with CO₂ to form the metal carbonate and

What the problem is asking

You are told that each hydroxide base reacts with $CO_2$ to make the corresponding metal carbonate plus water. So you need to write the correct products and then balance atoms on both sides.

Identify the products from the words

• Lithium hydroxide forms lithium carbonate: $Li_2CO_3$
• Sodium hydroxide forms sodium carbonate: $Na_2CO_3$
• Water is $H_2O$

So the unbalanced skeleton equations are: $$LiOH + CO_2 \rightarrow Li_2CO_3 + H_2O$$ $$NaOH + CO_2 \rightarrow Na_2CO_3 + H_2O$$

Balancing the lithium hydroxide reaction

Start by balancing the metal (Li). Since the product has $Li_2$, put a 2 in front of $LiOH$: $$2LiOH + CO_2 \rightarrow Li_2CO_3 + H_2O$$ Now check each element:

• Li: $2$ on left, $2$ on right
• C: $1$ on left, $1$ on right
• H: $2$ on left, $2$ on right (in $H_2O$)
• O: left has $2$ (from $2LiOH$) $+$ $2$ (from $CO_2$) $=4$; right has $3$ (in $Li_2CO_3$) $+$ $1$ (in $H_2O$) $=4$ So it is balanced.

Balancing the sodium hydroxide reaction

Use the same idea: the carbonate has $Na_2$, so you need $2NaOH$. $$2NaOH + CO_2 \rightarrow Na_2CO_3 + H_2O$$ Atom check:

• Na: $2$ and $2$
• C: $1$ and $1$
• H: $2$ and $2$
• O: $2+2=4$ and $3+1=4$ Balanced.

Quick pattern to remember

For an alkali metal hydroxide $MOH$ reacting with carbon dioxide to form carbonate, the balanced pattern is: $$2MOH + CO_2 \rightarrow M_2CO_3 + H_2O$$ where $M$ is $Li$ or $Na$.