Qstnid -A-10-boiling Point Of Water At 750 Mm Hg Is 99.63°c. How Much Sucrose Is To Be Added To 500 G Of Water Such That It Boils At 100°c. Molal Elevation Constant For Water Is 0.52 K Kg Mol<sup>-1</sup>. - 02: Solutions - Neet-xii-chemistry

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02: Solutions

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#10
Boiling
point of water at 750 mm Hg is 99.63°C. How much sucrose is to be
added to 500 g of water such that it boils at 100°C.
Molal elevation constant for water is 0.52 K kg mol^-1.
Ans : Here,
elevation of boiling point ΔT_b = (100 + 273) - (99.63 + 273)
=
0.37 K
Mass
of water, w_l = 500 g
Molar
mass of sucrose (C₁₂H₂₂O₁₁), M₂ = 11 × 12 + 22 × 1 + 11 × 16
=
342 g mol^-1
Molal
elevation constant, K_b = 0.52 K kg mol^-1
We
know that:

=
121.67 g (approximately)
Hence,
121.67 g of sucrose is to be added.
Note: There is a slight variation in this answer and the one given in the
NCERT textbook.