Question

A compound has the empirical formula chcl. a 256 ml flask, at 373 k and 750. torr, contains 0.800 g of the gaseous compound. give the molecular formula. (type your answer using the format ch4 for ch4.)

Answer 1

From the ideal gas law,
n = PV / RT
n= moles = W / M
W= weight
M = molar mass

So, W / M = PV /RT
=> M = WRT / PV
We got above the formula for molar mass.

Now, put the appropriate values.

W= 0.8 g 
R=0.0821 atm / K-mol
T= 373 K
V= 256mL = 0.256 L 
P = 750 torr =  750 / 760 = 0.987 atm

After putting these values and calculating the value of M, we get :

M  = 97 g / mol

Now, Assuming the molecular formula is $(CHCl)_n$

So, molar mass = n × (12.01 + 1.01 + 35.45)

equate it with 97.

We get the value of n then:
n×(12.01 + 1.01 + 35.45) = 97

n = 2

Means molecular formula is $C_2H_2Cl_2$