Question #1fd4c

2 Answers
Feb 25, 2018

The molecular formula is C_4H_10

Explanation:

n= V/24 = 9.6/24 = 0.4mol

Mr = M/n = 23.2/0.4 = 58 gmol^-1

Since the formula mass of C_2H_5 is 29, it follows that the molecule contains 58/29, or 2 times the number of atoms.

Hence, the molecular formula is C_4H_10, which is butane.

Feb 25, 2018

The molecular formula is "C"_4"H"_10, which is probably butane.

Explanation:

We have "C"_2"H"_5 as the empirical formula. We must find its molar mass. To do so, we need to know how many moles of it evaporated. Use the Ideal Gas Law:

PV=nRT, and here:

P=1"atm"

V=9.6"L"

R=0.0821"L atm K"^-1"mol"^-1

T=293.15"K".

To solve for n, moles, we rearrange:

n=(PV)/(RT), and inputting:

n=(1*9.6)/(293.15*0.0821)

n=0.399"mol"~~0.4"mol"

Another formula for moles is n=m/M, where m is the mass and M the molar mass.

Rearranging to solve for M, we get:

M=m/n

We have m=23.2"g". Inputting:

M=23.2/0.399

M=58.16"g/mol"

We must calculate the molar mass of the empirical formula:

M_e=(12*2)+(1*5)

M_e=29"g/mol"

We see a 2:1 ratio.

Therefore, the molecular formula is "C"_4"H"_10, which is probably butane.