The mass of urea that would be dissolved in 180g of water in order to produce the same lowering of vapour pressure as is produced by dissolving 19g of cane sugar (c12 h22 o11) in 100g water is

Asked by KRISHPATEL.soc | 21st Jun, 2021, 05:58: PM

Expert Answer:

Lowering of Vapour pressure is calculated by-
fraction numerator straight P subscript straight o minus straight P subscript straight s over denominator straight P subscript straight s end fraction equals straight n subscript solute over straight n subscript solvent
Vapour space pressure space when space 19 space straight g space of space cane space sugar space in space 100 space straight g space of space water space is space calculated space by minus

fraction numerator 760 minus straight P subscript straight s over denominator straight P subscript straight s end fraction equals fraction numerator begin display style fraction numerator 19 over denominator 144 plus 22 plus 176 end fraction end style over denominator begin display style 100 over 18 end style end fraction
fraction numerator 760 minus straight P subscript straight s over denominator straight P subscript straight s end fraction equals fraction numerator begin display style 19 over 342 end style over denominator begin display style 100 over 18 end style end fraction

fraction numerator 760 minus straight P subscript straight s over denominator straight P subscript straight s end fraction equals fraction numerator 0.0555 over denominator 5.55 end fraction

fraction numerator 760 minus straight P subscript straight s over denominator straight P subscript straight s end fraction equals 1 over 100
76000 minus 100 straight P subscript straight s equals straight P subscript straight s
101 straight P subscript straight s equals 7600
straight P subscript straight s equals 7600 over 101 equals 75.427 space mm space of space Hg
Lowering space of space pressure equals fraction numerator 760 minus 75.427 over denominator 75.427 end fraction equals fraction numerator 684.573 over denominator 75.427 end fraction equals 9.075

Lowering space of space pressure space is space same space in space solution space of space urea space in space water
Molar space mass space of space urea equals 60 space straight g divided by mol

9.075 equals fraction numerator begin display style straight x over 60 end style over denominator begin display style 18 over 180 end style end fraction
9.075 equals fraction numerator begin display style straight x over 60 end style over denominator begin display style 1 over 10 end style end fraction
straight x equals 6 cross times 9.075 equals 54.55 space straight g

Mass space of space Urea equals 54.55 space straight g

Answered by Ravi | 22nd Jun, 2021, 10:30: AM