Question

A 258-ml sample of mek, an industrial solvent, is found to have a mass of 0.599 g at and 100c. what is the molar mass of mek?

Answer 1

The ans is 71.1 g/mol

Step-by-step explanation:

Mass of MEK (m) = 0.599 g

Volume of MEK (V) = 258 ml = 0.258 L

Temperature (T) = 100 C = 100 +273 = 373 K

Pressure = 1 atm

Based on the ideal gas equation:

`PV = nRT`

where n = number of moles and R = gas constant 0.0821 Latm/mol-K

`n = (PV)/(RT)`

`n = (1*0.258)/(0.0821*373) = 0.00842 moles`

number of moles is given as:

`n = (mass MEK)/(molar mass MEK) \\\\molar mass = (mass MEK)/(n) = (0.599)/(0.00842)  = 71.14 g/mol`

Answer 2

Correct answer is : 72.0 g/mole If we assume Ideal Gas Law, PV = nRT. n = PV/RT = ((0.988 atm)*(0.258 L))/((0.0821 L*atm/mole*K)*(100 + 273.15)) = 0.00832 moles Molar mass = 0.599 g/0.00832 moles = 72.0 g/mole; your answer is E.