A closed vessel with volume of 226.9mL initially contained air at 680.8mmHg at 16.5 degrees celcius.
A sample of an organic liquid of mass 0.113g was injected into the flask which was then warmed to 124.9 degrees celcus causing all the organic liquid to vaporise. The final pressure inside the container was then 1268.7mmHg. (give answers to 1 decimal point):
a) air pressure inside at 124.9 degrees celcius? _____mmHg
b) pressure due to organic vapour at 124.9 degrees celcius? ____mmHg
c) Molar mass of organic compound? ____g mol^-1
Note the correct spelling of celsius.
a. Use P1/T1 = P2/T2 to calculate the pressure due to the air at the new temperature.
b. Total pressure @ 124.9 - pressure air @ 124.9 = pressure organic liquid @ 124.9
c. Use PV = nRT. Use P of organic liquid in atmospheres, don't forget to change T to Kelvin, and calculate n = number of moles.
Then moles = grams/molar mass.
Post your work if you get stuck.
i did p1/t1 =p2/t2 converted celsius to kelvin
i get 935.5 mmHg for a
then 333.2 for b
i don't get c
To solve this problem, we can use the Ideal Gas Law equation: PV = nRT.
First, let's solve for the number of moles of air in the closed vessel before the injection of the organic liquid:
a) To find the air pressure inside at 16.5 degrees Celsius, we need to convert the temperature to Kelvin. The equation to convert Celsius to Kelvin is: K = °C + 273.15.
So, the initial temperature in Kelvin is: 16.5°C + 273.15 = 289.65 K.
Now, we can use the ideal gas law equation to calculate the number of moles of air:
PV = nRT
(680.8 mmHg)(0.2269 L) = n(0.0821 L·atm/(K·mol))(289.65 K)
Solving for n, we have:
n = (680.8 mmHg)(0.2269 L) / (0.0821 L·atm/(K·mol))(289.65 K)
n ≈ 0.026 mol
b) Next, let's calculate the pressure due to the organic vapor at 124.9 degrees Celsius. Again, we need to convert the temperature to Kelvin:
Temperature in Kelvin = 124.9°C + 273.15 = 397.05 K.
Using the ideal gas law equation, we can find the new pressure:
(1268.7 mmHg)(0.2269 L) = n(0.0821 L·atm/(K·mol))(397.05 K)
Solving for n, we have:
n = (1268.7 mmHg)(0.2269 L) / (0.0821 L·atm/(K·mol))(397.05 K)
n ≈ 0.0783 mol
c) Finally, to find the molar mass of the organic compound, we can use the formula:
Molar mass = (Mass of the organic liquid) / (Number of moles)
The mass of the organic liquid is given as 0.113 g, and we found the number of moles to be approximately 0.0783 mol.
Molar mass = 0.113 g / 0.0783 mol ≈ 1.4 g/mol
So, the molar mass of the organic compound is approximately 1.4 g/mol.