I am unsure of how to approach this question, any help would be greatly appreciated!
"2.085g of PCl5 were heated to 250°C in a 500mL vessel:
PCl5 (g) ⇌ PCl3 (g) + Cl2 (g)
Calculate the initial concentration of PCl5. At equilibrium the concentration of the chlorine is 0.018 mol L-1."
This is a weirdo question. The initial concn is
mols PCl5 = grams/molar mass
M = mols/0.500 = ?
The other numbers are not needed. They would be needed if you wanted the equilibrium concn of PCl5.
To calculate the initial concentration of PCl5, we need to use the given information and the concept of stoichiometry.
First, we need to convert the given mass of PCl5 (2.085g) to moles. We can do this using the molar mass of PCl5, which is the sum of the atomic masses of its elements:
Molar mass of P = 31 g/mol
Molar mass of Cl = 35.5 g/mol
Molar mass of PCl5 = (1 * 31 g/mol) + (5 * 35.5 g/mol) = 208.5 g/mol
Now, we can calculate the number of moles of PCl5:
moles of PCl5 = mass of PCl5 / molar mass of PCl5
moles of PCl5 = 2.085g / 208.5 g/mol
Next, we need to convert the volume of the vessel (500 mL) to liters:
volume of vessel = 500 mL = 500/1000 L = 0.5 L
Now, we have all the necessary information to calculate the initial concentration of PCl5. The initial concentration (denoted as [PCl5]) is given in moles per liter.
initial concentration of PCl5 = moles of PCl5 / volume of vessel
initial concentration of PCl5 = (2.085g / 208.5 g/mol) / 0.5 L
After performing the calculations, you will get the initial concentration of PCl5.
Keep in mind that this is only the initial concentration. To calculate the equilibrium concentration of PCl5, you would need to consider the stoichiometry of the reaction and the given concentration of chlorine at equilibrium.