We observe that 7 grams of a gaseous com-
pound occupies 2102 mL at 49�C and 626 torr.
What is the molecular weight of the com-
pound?
Use PV = nRT and solve for n = number mols. Then n = grams/molar mass. You have n and grams, solve for molar mass.
I did 662(2.102)=n(62.37)(322) and got n=.069288. then I divided n by 7 and got 101.020 g/mol, but that is incorrect. I do not understand what i did wrong.
I wonder if you transposed your numbers for pressure. You have 626 in the problem but 662 in your work. If I run 626 torr through the calculations I get 0.065 something. Then 7/n = molar mass = appoximately 106. (I think you did 7/n but that isn't what you said you did.)
To calculate the molecular weight of the compound, we need to use the ideal gas law equation:
PV = nRT
Where:
P = pressure (in atm or torr)
V = volume (in liters or mL)
n = moles of gas
R = ideal gas constant (0.0821 L·atm/mol·K or 62.36 torr·mL/mol·K)
T = temperature (in Kelvin)
In this case, we are given the values for pressure (626 torr), volume (2102 mL), temperature (49ºC), and need to find the moles of gas. Once we have the moles of gas, we can calculate the molecular weight.
Step 1: Convert the temperature to Kelvin:
T (K) = T (ºC) + 273.15
T (K) = 49 + 273.15 = 322.15 K
Step 2: Convert the volume from mL to liters:
V (L) = V (mL) / 1000
V (L) = 2102 mL / 1000 = 2.102 L
Step 3: Convert the pressure to atm:
P (atm) = P (torr) / 760
P (atm) = 626 torr / 760 = 0.822 atm
Step 4: Use the ideal gas law equation to find the moles of gas:
PV = nRT
n = (PV) / (RT)
n = (0.822 atm * 2.102 L) / (0.0821 L·atm/mol·K * 322.15 K)
n ≈ 0.091 mol
Step 5: Calculate the molecular weight:
Molecular weight = mass / moles
Molecular weight = 7 grams / 0.091 mol
Molecular weight ≈ 76.9 g/mol
Therefore, the molecular weight of the compound is approximately 76.9 g/mol.