Question

The air in a manned spacecraft or submarine needs to be purified of exhaled carbon dioxide. Write equations for the reactions between carbon dioxide and (a) lithium oxide \(\left(\mathrm{Li}_{2} \mathrm{O}\right),(\mathrm{b})\) sodium peroxide \(\left(\mathrm{Na}_{2} \mathrm{O}_{2}\right),\) and (c) potassium superoxide \(\left(\mathrm{KO}_{2}\right)\)

Short answer

(a) CO₂ + Li₂O → Li₂CO₃ (b) 2CO₂ + 2Na₂O₂ → 2Na₂CO₃ + O₂ (c) 4CO₂ + 4KO₂ → 2K₂CO₃ + 3O₂

Step-by-step solution

Reaction with Lithium Oxide

When carbon dioxide reacts with lithium oxide, the chemical equation for the reaction is:\[ ext{CO}_2 + ext{Li}_2 ext{O} \rightarrow ext{Li}_2 ext{CO}_3\]This reaction forms lithium carbonate.

Reaction with Sodium Peroxide

When carbon dioxide reacts with sodium peroxide, the chemical equation for the reaction is:\[2 ext{CO}_2 + 2 ext{Na}_2 ext{O}_2 \rightarrow 2 ext{Na}_2 ext{CO}_3 + ext{O}_2\]This reaction produces sodium carbonate and releases oxygen.

Reaction with Potassium Superoxide

When carbon dioxide reacts with potassium superoxide, the chemical equation is:\[4 ext{CO}_2 + 4 ext{KO}_2 \rightarrow 2 ext{K}_2 ext{CO}_3 + 3 ext{O}_2\]This reaction forms potassium carbonate and releases oxygen gas.

Key concepts

Carbon Dioxide Absorption

Carbon dioxide absorption is a critical process in closed environments like spacecraft and submarines. This is because humans exhale carbon dioxide which must be removed to maintain safe and breathable air.
Chemical reactions are employed to absorb or react with the carbon dioxide, converting it into a less harmful or inert substance.
Usually, compounds such as lithium oxide, sodium peroxide, and potassium superoxide are used. These compounds react with carbon dioxide and help purify the air by converting CO e 2 into other compounds like carbonates.

• Absorbing CO e 2 prevents its accumulation in the air.
• The process is essential in environments where refreshing the air is not feasible.
• Ensuring effective CO e 2 removal helps maintain a stable living environment.

Understanding these absorption reactions helps in engineering systems that purify air effectively.

Lithium Oxide Reaction

When carbon dioxide reacts with lithium oxide, it results in the formation of lithium carbonate. The equation for this chemical reaction is:
\[ \text{CO}_2 + \text{Li}_2\text{O} \rightarrow \text{Li}_2\text{CO}_3 \]
Lithium oxide (Lie 2O) is commonly used in air purification systems. Its reaction with carbon dioxide is straightforward and efficient.

• This reaction does not produce oxygen gas unlike some other reactions.
• Lithium carbonate, the product, is a stable compound.

Using lithium oxide is particularly advantageous in controlled environments due to its simplicity and reliability.

Sodium Peroxide Reaction

Reacting carbon dioxide with sodium peroxide results in sodium carbonate and releases oxygen gas. The balanced equation is:
\[ 2\text{CO}_2 + 2\text{Na}_2\text{O}_2 \rightarrow 2\text{Na}_2\text{CO}_3 + \text{O}_2 \]
Sodium peroxide is widely utilized due to its dual benefit of CO2 absorption and oxygen production.

• This reaction is beneficial as it generates oxygen gas, which is vital for breathing.
• The resultant product, sodium carbonate, is also stable and non-toxic.

The generation of oxygen from sodium peroxide makes it an attractive option for use in life-support systems.

Potassium Superoxide Reaction

In environments requiring strict air quality controls, potassium superoxide's reaction with carbon dioxide is invaluable. The reaction equation is:
\[ 4\text{CO}_2 + 4\text{KO}_2 \rightarrow 2\text{K}_2\text{CO}_3 + 3\text{O}_2 \]
Potassium superoxide (KOe 2) reacts with COe 2 to form potassium carbonate and simultaneously liberates oxygen gas.

• The release of significant amounts of oxygen is crucial.
• Potassium carbonate formed is inert and non-hazardous.

Employing potassium superoxide enhances both COe 2 removal and oxygen replenishment, making it especially suited to hostile or closed environments.