1.

35 % (W/W) solution of ethylene glycol in water, an anti-freezer used in automobiles in radiators as a coolant. It lowers freezing point of water to -17.6 °C. Calculate the mole fraction of the components.

Answer»

35% (W/W) means 100 g solution contains 35 g ethylene glycol (CH2OH-CH2OH) and 65 g H2O.

Molar mass of water = 18 g mol-1

Molar mass of ethylene glycol (CH2OHCH2OH) = 62 g mol-1

Number of moles of water = n1 = \(\frac{65}{18}\) = 3.611 mol

Number of moles of ethylene glycol = n2\(\frac{35}{62}\)= 0.5645 mol

Total moles = n = n1 + n2 

= 3.611 + 0.5645 

= 4.1755 mol

Mole fraction of ethylene glycol = x2

\(\frac{n_2}{n_1}\) \(\frac{0.5645}{4.1755}\) = 0.1352

∴ Mole fraction of water = 1 – x2 = 1 – 0.1352

= 0.8648

∴ Mole fraction of water = 0.8648 Mole fraction of ethylene glycol = 0.1352



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