Answer:
The answer to the question is
- The pressure in the flask if no chemical reaction were to occur is 0.6406 atm
- The partial pressure of PCl₅ and PCl₃ in the flask at 252 °C is 0.3594 atm each
Explanation:
To solve the question we list the knowns so as to plug in the values when required
Mass of PCl₅ = 6.19g
Volume of flask = 2.00 L
Temperature 252 °C = 525.15 K
Molar mass of PCl = 208.24 g/mol
Therefore the number of moles of PCl₅ = (6.19 g)/(208.24 g/mol) =moles2.973×10⁻²
PV = nRT therefore P = nRT/V = (2.973×10⁻² moles×8.314 J/(gmol·K)× 525.15 K)/(0.002 m³) = 64906.01 Pa = 0.6406 ATM
(2) At 252 °C the PCl₅ dissociates partially as follows
PCl₅↔PCl₃+Cl₂
New pressure is observed to be 1.00 atm
Dalton's law states that = P₁ + P₂ +...+Pₙ where P₁, P₂, Pₙ are the partial pressures of the constituent gases
That means = P(PCl₅) + P(PCl₃) + P(Cl₂)
The difference in pressure due to the dissociation = 1 - 0.6406 = 0.3594 ATM, However 1 PCl dissociates into 2 moles of gases
That is Y-X +2X = 1 ATM where Y = 0.6406 ATM then X = 0.3594 ATM
Therefore the final partial pressure of PCl₅ = 0.6406-0.3594 = 0.2812 atm
and P(PCl₃) and P(Cl₂) = 0.3594 ATM each