If 0.385 g of a gas occupies a volume of 200mL at minus 73 degrees C and 750 torr, what is the molecular mass of the gas?
PV = nRT
then n = g/molar mass. Post your work if you get stuck.
So far I have: (0.385g)(8.31dm3 times kPa)(200K)(1000cm3)/(7.40 kPa)(mol times K)(200 cm3)(1Dm3) which =639870 g/1480 mol which =432.345 and that is not even close to one of the answers. I don't know where I am going wrong.
I think your units are messed up.
PV = nRT
It's easier to use atmospheres than kPa. R is 0.08205 L*atm/mol*K when atm is used for pressure, P. V must be in liters. I don't know what grams is doing in PV = nRT
P = 750 torr/760 = ?? atm
V = 200 mL = 0.200 L
n = solve for this
R = 0.08205
T in K = 273 + C = 273-73 = 200 K
So
(750/760)atm x 0.200 L = n x 0.08205 L*atm/mol*K x 200 K.
Solve for n, THEN,
n = # mols = grams/molar mass.
You have mols and grams, solve for molar mass. I hope this helps.
To find the molecular mass of the gas, 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 temperature from Celsius to Kelvin:
T(K) = T(C) + 273.15
T(K) = -73 + 273.15
T(K) = 200.15 K
Now, let's convert the volume from mL to L:
V(L) = V(mL) / 1000
V(L) = 200 mL / 1000
V(L) = 0.2 L
Next, let's convert the pressure from torr to atm:
P(atm) = P(torr) / 760
P(atm) = 750 torr / 760
P(atm) = 0.9868 atm
Now, we can rearrange the ideal gas law equation to solve for n (number of moles):
n = (PV) / (RT)
Rearranging this equation, we get:
n = (P * V) / (R * T)
Substituting the given values, we have:
n = (0.9868 atm * 0.2 L) / (0.0821 L * atm/(mol * K) * 200.15 K)
Simplifying the equation, we get:
n = 0.002396 mol
Now, we can find the molecular mass (M) using the equation:
M = molar mass / number of moles
Rearranging this equation, we get:
molar mass = M * number of moles
Substituting the given values, we have:
molar mass = 0.385 g / 0.002396 mol
Simplifying the equation, we have:
molar mass = 160.59 g/mol
Therefore, the molecular mass of the gas is approximately 160.59 g/mol.