A 40.4 g sample of a gas with the empirical formula C5H12 occupied a volume of 3070 mL with a pressure of 5016.0 torr at 168 °C. Enter the molecular formula of the compound.

i calculated n from pv=nrt

but, when i divided it into 40.4 g of c5h12, i got the molar mass of the compound with is around 72.

after that, i had no idea what to do

You're there. The molar mass is 72 and C5H12 has a molar mass of 72 so the molecular formula is C5H12 and not a multiple of C5H12.

thank you!!

To determine the molecular formula of the compound, we need to first find the molar mass of the empirical formula C5H12.

1. Calculate the moles of the compound using the given mass and the molar mass of the empirical formula.
- Molar mass of C5H12 = (5 * atomic mass of C) + (12 * atomic mass of H)
- Atomic mass of C = 12.01 g/mol
- Atomic mass of H = 1.01 g/mol
- Molar mass of C5H12 = (5 * 12.01) + (12 * 1.01) g/mol

2. Use the ideal gas equation (PV = nRT) to find the number of moles (n) of the gas.
- P = pressure in atm (convert the given pressure of 5016.0 torr to atm by dividing by 760 torr/atm)
- V = volume in liters (convert the given volume of 3070 mL to liters by dividing by 1000 mL/L)
- T = temperature in Kelvin (convert the given temperature of 168 °C to Kelvin by adding 273.15)
- R = ideal gas constant = 0.0821 L.atm/(mol.K)
- Rearranging the equation, n = PV / RT

3. Divide the moles of the compound by the moles calculated in step 1 to find the value of "x" in the molecular formula.
- x = moles of compound / moles of empirical formula

4. Finally, multiply the subscripts of the empirical formula by "x" to get the molecular formula.

Let's calculate these steps:

Step 1:
Molar mass of C5H12 = (5 * 12.01) + (12 * 1.01) g/mol

Step 2:
P = 5016.0 torr / 760 torr/atm = ... (calculate the pressure in atm)
V = 3070 mL / 1000 mL/L = ... (calculate the volume in liters)
T = 168 °C + 273.15 = ... (calculate the temperature in Kelvin)

n = P * V / (R * T)

Step 3:
Calculate the moles of the compound.

Step 4:
Determine the molecular formula by multiplying the subscripts of the empirical formula by "x".