A 1.20-g sample of dry ice is added to a 755 mL flask containing nitrogen gas at a temperature of 25.0 °C and a pressure of 725 mmHg. The dry ice sublimes (converts from solid to gas), and the mixture returns to 25.0 °C. What is the total pressure in the flask?

Verified step by step guidance

1. Convert the mass of dry ice (CO₂) to moles using its molar mass (44.01 g/mol).
2. Use the ideal gas law, PV = nRT, to calculate the pressure exerted by the CO₂ gas. Use the moles of CO₂ calculated, the volume of the flask (755 mL converted to liters), the temperature in Kelvin (25.0 °C converted to 298.15 K), and the ideal gas constant R (0.0821 L·atm/mol·K).
3. Convert the initial pressure of nitrogen gas from mmHg to atm for consistency with the ideal gas law calculations.
4. Add the pressure exerted by the CO₂ gas to the initial pressure of the nitrogen gas to find the total pressure in the flask.
5. Ensure the final total pressure is expressed in the desired units, either atm or mmHg, by converting if necessary.

Key Concepts

Ideal Gas Law

The Ideal Gas Law relates the pressure, volume, temperature, and number of moles of a gas through the equation PV = nRT. This law is essential for understanding how gases behave under varying conditions and is crucial for calculating the total pressure in the flask after the dry ice sublimates.

Sublimation

Sublimation is the process where a solid transitions directly to a gas without passing through the liquid phase. In this scenario, dry ice (solid CO2) sublimates into gaseous CO2, contributing to the total pressure in the flask, which must be accounted for in the calculations.

Dalton's Law of Partial Pressures

Dalton's Law states that the total pressure of a gas mixture is equal to the sum of the partial pressures of each individual gas present. This concept is vital for determining the total pressure in the flask after the dry ice sublimates, as it allows for the addition of the partial pressure of the newly formed CO2 gas to the existing nitrogen gas pressure.