Question

on place un bloc de glace sèche (du dioxyde de carbone solide) de 5.6 g dans un contenant de 4.0 l qui ne contient rien dautre (à 27.0 °c). quand la totalité du dioxyde de carbone est passée à létat gazeux, quelle est la pression dans le contenant? si on place les 5.6 g de dioxyde de carbone solide dans le même contenant, mais que celui - ci contient déjà de lair à 99.0 kpa, quelle est la pression partielle du dioxyde de carbone et la pression totale dans le contenant quand la totalité du dioxyde de carbone est passée à létat gazeux?

Explanation:

Step1: Calculate moles of CO₂

The molar - mass of CO₂ is $M = 12.01+2\times16.00=44.01\ g/mol$. The number of moles $n$ of CO₂ is calculated by $n=\frac{m}{M}$, where $m = 5.6\ g$. So $n=\frac{5.6\ g}{44.01\ g/mol}\approx0.127\ mol$.

Step2: Convert temperature to Kelvin

The temperature $T=(27.0 + 273.15)\ K=300.15\ K$ and the volume $V = 4.0\ L=4.0\times10^{- 3}\ m^{3}$.

Step3: Use the ideal - gas law to find pressure in an empty container

The ideal - gas law is $PV = nRT$, where $R = 8.314\ J/(mol\cdot K)$. Solving for $P$, we get $P=\frac{nRT}{V}$. Substituting the values: $P=\frac{0.127\ mol\times8.314\ J/(mol\cdot K)\times300.15\ K}{4.0\times10^{-3}\ m^{3}}$.
$P=\frac{0.127\times8.314\times300.15}{4.0\times10^{-3}}\ Pa\approx79300\ Pa = 79.3\ kPa$.

Step4: Find partial pressure of CO₂ in a container with air

The partial pressure of CO₂ when the container already has air is the same as the pressure in the empty container because the partial pressure of a gas in a mixture is determined by its own amount, volume, and temperature according to the ideal - gas law. So the partial pressure of CO₂ is $P_{CO_2}=79.3\ kPa$.

Step5: Find total pressure

The total pressure $P_{total}$ is the sum of the partial pressure of air and the partial pressure of CO₂. Given $P_{air}=99.0\ kPa$ and $P_{CO_2}=79.3\ kPa$, then $P_{total}=P_{air}+P_{CO_2}=99.0\ kPa + 79.3\ kPa=178.3\ kPa$.

Answer:

The pressure in the empty container is approximately $79.3\ kPa$. The partial pressure of CO₂ in the container with air is $79.3\ kPa$, and the total pressure is $178.3\ kPa$.