the vapor from an unknown volatile liquid occupies a 269 ml. Erlenmeyer flask at 98.7 C and 748 mm Hg. The mass of the vapor is 0.791 g.
A. how many moles of vapor are present?
B. What is the molar mass of the volatile liquid?
a mole of ANY gas (vapor) occupies a volume of 22.4 L at STP
... 0º C and 1.00 atm
A. make the corrections for temperature and pressure to find the moles
B. divide the given mass by the moles from A. to find the molar mass
To answer these questions, we need to 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. We also need to convert the given values to the appropriate units.
A. To find the number of moles of vapor (n), we can rearrange the ideal gas law equation to solve for n: n = PV / RT.
Given:
Volume (V) = 269 mL = 0.269 L (converted to liters)
Pressure (P) = 748 mmHg (given)
Temperature (T) = 98.7 °C + 273.15 (converted to Kelvin)
Ideal gas constant (R) = 0.0821 L•atm/mol•K (standard value)
Now, we can substitute the values into the equation: n = (748 mmHg * 0.269 L) / (0.0821 L•atm/mol•K * (98.7 °C + 273.15)). Remember that mmHg is equivalent to torr.
B. To find the molar mass of the volatile liquid, we can use the formula: molar mass = mass / moles.
Given:
Mass = 0.791 g (given)
Number of moles (n) is determined in part A.
Now, substitute the values:
Molar mass = 0.791 g / number of moles.
To obtain the final answer, calculate the molar mass using the given values for mass and the number of moles found in part A.