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

See above.

To solve this problem, we can use the ideal gas law equation: PV = nRT, where P is the pressure, V is the volume, n is the number of moles, R is the ideal gas constant, and T is the temperature in Kelvin.

First, let's convert the given temperatures from Celsius to Kelvin:
Initial temperature = 16.5 degrees Celsius + 273.15 = 289.65 K
Final temperature = 124.9 degrees Celsius + 273.15 = 398.05 K

a) To find the air pressure inside at 124.9 degrees Celsius, we need to assume that the volume remains constant. Since only the temperature changes, we can use the combined gas law equation, PV/T = constant.

Initial pressure * Initial temperature = Final pressure * Final temperature
(680.8 mmHg) * (289.65 K) = (New pressure) * (398.05 K)

Now, solve for the new pressure inside the container:
New pressure = (680.8 mmHg * 289.65 K) / 398.05 K
New pressure ≈ 496.6 mmHg

Therefore, the air pressure inside the container at 124.9 degrees Celsius is approximately 496.6 mmHg.

b) To find the pressure due to the organic vapor at 124.9 degrees Celsius, we need to find the change in pressure. The final pressure inside the container (1268.7 mmHg) is the combination of the air pressure (496.6 mmHg) and the pressure due to the organic vapor.

Pressure due to organic vapor = Final pressure - Air pressure
Pressure due to organic vapor = 1268.7 mmHg - 496.6 mmHg
Pressure due to organic vapor ≈ 772.1 mmHg

Therefore, the pressure due to the organic vapor at 124.9 degrees Celsius is approximately 772.1 mmHg.

c) To find the molar mass of the organic compound, we need to use the ideal gas law equation. Rearrange the equation to solve for the number of moles (n):

PV = nRT

Rearranging:
n = PV / RT

First, we need to find the number of moles of the organic vapor. We can use the ideal gas law equation with the known values:
P = Pressure due to organic vapor = 772.1 mmHg
V = Volume of the flask = 226.9 mL = 0.2269 L
R = Gas constant = 0.0821 L·atm/(mol·K)
T = Final temperature = 398.05 K

Now, substitute these values into the equation:
n = (772.1 mmHg * 0.2269 L) / (0.0821 L·atm/(mol·K) * 398.05 K)

To get the molar mass, we need to divide the mass of the organic compound (0.113 g) by the number of moles we just calculated:

Molar mass = Mass of organic compound / Number of moles

Molar mass = 0.113 g / number of moles

Now, substitute the calculated number of moles:
Molar mass ≈ 0.113 g / number of moles

Calculate the number of moles using the previously determined formula and then substitute it to get the molar mass of the organic compound.