1.82g of glucose is dissolved in 25g of water .calculate the molalityand mole fraction of glucose and water
Answers
Molality of a substance can be calculated as follows:
Molality = moles of solute (glucose)
mass of solvent (water)
moles of glocose---
C6H1206 molar mass= (12x6)+(1x12)+(16x6)
= 72+ 12 + 96
= 180
mass of C6H12O6= 1.82g
therefore moles= 1.82/180
= 0.01 moles
Therefore its Molality =
moles of glucose(0.01)/ mass of water(0.025kg)
0.01/0.025 = 0.4 molal
molality = 0.4 molal
b) Mole fraction
find mole of glucose and that of water, calculte fraction.
moles of glucose= 0.01
moles of water=
25mass/ molar mass mass= 25g
molar mass H2O= (1x2) +16 = 2+16 =18
moles = 25/18
= 1.388
moles of glucose = 0.01
moles of water = 1.388
mole fraction of glucose = mole of glucose = 0.01 = 7.2 x10^-3 mole of water 1.388
Therefore mole fraction of glucose= 72 = 9
10000 1250
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