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

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Explanation:

Vapor Pressure lowering is governed by Raoult's law, which basically states:
#P_n = (X_n)xxP_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#(1 - P_n/P_o)#, which is #(1-X_n)#

#X_n = ("moles of water")/("total moles")#
#X_n = 10/10.1 = 0.99009901#

Relative Lowering:
#(1-0.99009901) = 0.00990099 = 0.01#