A sample of an unknown volatile liquid was injected into a Dumas flask (mass of flask=

27.0928 g. Volume of the flask is 0.1040L) and heated until no visible traces of the

liquid could be found. The flask and its contents were then rapidly cooled and

reweighed (mass of flask + vapor = 27.4593 g). The atmospheric pressure and

temperature during the experiment were 0.976 atm and 18.0°C, respectively. The

unknown volatile liquid was_ (make sure you use the proper name for this

organic compound)

Ethyl acetate.

Explanation:

We can use the general law of ideal gas: PV = nRT.

where, P is the pressure of the gas in atm (P = 0.976 atm).

V is the volume of the gas in L (V = volume of the flask = 0.1040 L).

n is the no. of moles of the gas in mol (n = ? mol).

R is the general gas constant (R = 0.0821 L. atm/mol. K),

T is the temperature of the gas in K (T = 18.0°C + 273 = 291 K).

∴ n = PV/RT = (0.976 atm) (0.1040 L) / (0.0821 L. atm/mol. K) (291 K) = 4.25 x 10⁻³ mol.

∵ n = mass/molar mass,

mass of the volatile liquid = (mass of flask + vapor) - (mass of flask) = 27.4593 g - 27.0928 g = 0.3665 g.

∴ Molar mass of the volatile liquid = (mass) / (n) = (0.3665 g) / (4.25 x 10⁻³ mol) = 86.235 g/mol.

The volatile liquid may be ethyl acetate which has a molar mass of (88.11 g/mol).