Question

Which one of the following statements is false?

• A. Raoulfs law states that the vapour pressure of a component over a solution is proportional to its mole fraction
• B. The osmotic pressure $(\pi )$ of a solution is given by the equation $\pi =MRT,$ where M is the molarity of the solution
• C. The correct order of osmotic pressure for 0.01 M aqueous solution of each compound is $BaC{l}_2>KC1>C{H}_{3}COOH>sucrose$
• D. Two sucrose solutions of same molality prepared in different solvents will have the same freezing point depression

Answer 1

Answer: (D)

(a) $p_A=X_A{P}_A^o$ true (b) $\pi =iMRT=MRT$ true (if vant Hoff factor $i=1$ ) (c) $i=[1+(y-1)x]$ $y=$ number of ions $x=$ degree of ionisation $i=3$ for $BaC{l}_{2}x=1$ (strong electrolyte) $i=2$ for $KClx=1$ (strong electrolyte) $i=(1+x)$ for $C{H}_{3}COOHx<<1$ (weak) $i=1$ for sucrose (non-electrolyte) $i$ (for $BaC{l}_2$ ) $>KCl>C{H}_{3}COOH>sucrose$ Thus, is also true. (d) $\Delta T_f=K_{f}m.$ $K_f$ is dependent on solvent. Thus, freezing points [ $=T$ (solvent) $-\Delta T_f$ ) are different. Thus, (d) is false.