Solution

A solution of glucose in water is labelled as 10% w/ w, what would be the molality and mole fraction of each component in the solution? If the density of solution is 1.2 g mL^-1, then what shall be the molarity of the solution?

Ans: Mass of solute (W_B) = 10 g

Mass of solvent (W_A) = 90 g

Molar mass of solute (M_B) = 180 g/mol

Density of solution = 1.2 g/mL

Molality (m) = $\displaystyle \frac{{{{W}<em>{B}}}}{{{{M}</em>{B}}}}\times \frac{{1000}}{{{{W}_{A}}}}$ = $\displaystyle \frac{{10}}{{180}}\times \frac{{1000}}{{90}}$ = 0.62 m

Density = $\displaystyle \frac{{Mass}}{{Volume}}$ ⇒ Volume = $\displaystyle \frac{{Mass}}{{Density}}$ = $\displaystyle \frac{{100}}{{1.2}}$

Molarity = $\displaystyle \frac{{{{W}<em>{B}}}}{{{{M}</em>{B}}}}\times \frac{{1000}}{{v(ml)}}$ = $\displaystyle \frac{{10}}{{180}}\times \frac{{1000}}{{100}}\times 1.2$ = 0.66 M

H2S, a toxic gas with rotten egg like smell, is used for the qualitative analysis. If the solubility of H2S in water at STP is 0.195 m, calculate Henry’s law constant.

Answer

It is given that the solubility of H2S in water at STP is 0.195 m, i.e., 0.195 mol of H2S is

dissolved in 1000 g of water.

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Important NCERT Question of Chemistry

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