Chemistry, asked by honney9998, 1 year ago

In an experiment,18.04 of mannitol where dissolved in 100 g of water. the vapour presure of water was lowered by 0.309 mm Hg from 17.535 mm Hg calculate molar mass of mannitol

Answers

Answered by IlaMends
19

Answer: The molar mass of mannitol is 185.78 g/mol.

Explanation:

pressure of the solution= p_s=17.535 mm Hg

Pressure of the pure water =p_o-p_s=0.309 mmHg

p_o=0.306 mmHg+17.535 mmHg=17.841 mmhg

\frac{p_s}{p_o}=\chi_w=\frac{17.535 mmHg}{17.841 mmHg}=0.9828

\chi_w=\frac{n_w}{n_w+n_m}

0.9828=\frac{\frac{100 g}{18 g/mol}}{\frac{100 g}{18 g/mol}+n_m}

Number of moles of mannitol is the solution = n_m=0.0971 mol

n_m=0.0971 mol=\frac{\text{Mass of the mannitol}}{\text{Molar mass of the mannitol}(M)}=\frac{18.04 g}{M}

Molar mass of the mannitol =\frac{18.04 g}{0.0971 mol}=185.78 g/mol

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