Question

question 3
1 pts
when gaseous phosphorus pentachloride, pcl₅, is heated to moderate temperatures, it decomposes in to the gaseous phosphorus trichloride and chlorine gas. given that 87.9 kj of heat is consumed in the process at a constant pressure of 1.18 atm, what is the balanced thermochemical equation for this reaction? fill in the values for the coefficients (if the coefficient is 1, enter the number 1, do not leave blank), phase labels, and enthalpy.
pcl₅() → pcl₃() +
cl₂(); δh = kj

Explanation:

Step1: Write the un - balanced equation

The reaction is \(PCl_{5}\) decomposing into \(PCl_{3}\) and \(Cl_{2}\). The un - balanced equation is \(PCl_{5}(g)\to PCl_{3}(g)+Cl_{2}(g)\)

Step2: Balance the equation

By counting the number of atoms, we find that the equation \(PCl_{5}(g)\to PCl_{3}(g)+Cl_{2}(g)\) is already balanced (1 P atom, 5 Cl atoms on both sides)

Step3: Determine the sign of \(\Delta H\)

Since heat is consumed (endothermic reaction), \(\Delta H> 0\). Given that 87.9 kJ of heat is consumed when the reaction occurs as written (1 mole of \(PCl_{5}\) decomposes), \(\Delta H = + 87.9\) kJ

Answer:

1 \(PCl_{5}(g)\) → 1 \(PCl_{3}(g)\) + 1 \(Cl_{2}(g)\); \(\Delta H=+87.9\) kJ