# 18g glucose is dissolved in 180g of water. The relative lowering of vapour pressure is ? a)1 b)1.8 c)0.01 d)0.001

Mar 21, 2018

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#### Explanation:

Vapor Pressure lowering is governed by Raoult's law, which basically states:
${P}_{n} = \left({X}_{n}\right) \times {P}_{o}$
were ${P}_{n}$ is the new vapor pressure, ${X}_{n}$ is the mole faction of the solvent, and ${P}_{o}$ is the pure solvent vapor pressure.

I think the relative lowering would be$\left(1 - {P}_{n} / {P}_{o}\right)$, which is $\left(1 - {X}_{n}\right)$

${X}_{n} = \left(\text{moles of water")/("total moles}\right)$
${X}_{n} = \frac{10}{10.1} = 0.99009901$

Relative Lowering:
$\left(1 - 0.99009901\right) = 0.00990099 = 0.01$