Answer:
The molecular formula of the compound is P2F4
Explanation:
Step 1: Data given
Mass of the compound = 0.2324 grams
Volume of container = 378 mL
Pressure at 77 °C = 97.3 torr
The gaseous PxFy was then reacted with an aqueous solution of calcium chloride, and all of the fluorine was converted to 0.2631 g of CaF2.
Molar mass CaF2 = 78.07 g/mol
Step 2: Calculate moles CaF2
Moles CaF2 = 0.2631 g/ 78.07 g/mol=0.003370
Step 3: Calculate moles F
For every 1 mol CaF2 we have 1 mol Ca2+ and 2 moles F-
moles F- = 2 * 0.003370=0.006740
Step 4: Calculate mass of F
mass F = 0.006740 mol * 19.00 g/mol=0.1281 g
Step 5: Calculate mass of P
mass P = mass of compound - mass of F = 0.2324 - 0.1281 =0.1043 g
Step 6: Calculate moles P
moles P = 0.1043 g/ 30.97 g/mol=0.003368 moles
Step 7: Calculate mol ratio
We divide by the smallest amount of moles
P: 0.003368/0.003368 =1
F: 0.006740/ 0.003368 =2
The empirical formula is PF2
The empirical formula has a molar mass of 68.97 g/mol
Step 8: Calculate moles of compound
p*V = n*R*T
n = (p*V)/(R*T)
⇒ with p = the pressure of the gas = 97.3 torr = 97.3/760 = 0.128 atm
⇒ with V = the volume of the gas = 0.378 L
⇒ with R = the gas constant = 0.08206 L*atm/K*mol
⇒ with T = the temperature = 77.0 °C = 350 Kelvin
Number of moles =(0.128 *0.378)/(0.08206*350)
Number of moles =
moles gas = pV/RT = 0.128 atm x 0.378 dm^3/ 0.08206x350 K=0.00168
Step 9: Calculate molar mass
Molar mass = mass / moles
Molar mass = 0.2324 grams / 0.00168 moles
Molar mass = 138 g/mol
Step 10: Calculate the molecular formula
138.0 / 68.97 = 2
2*(PF2) = P2F4
The molecular formula of the compound is P2F4
