Solutions - ISC Class 12 Chemistry Questions with Answers, Page 4

Colligative properties depend on:

A solution of sucrose (molecular weight 342 g mol-1) has been prepared by dissolving 68.4 g of sucrose in 1000 g of water. (Kf for water = 1.86 K kg mol-1)

If molality of the dilute solution of a non-volatile, non-dissociating and non-associating electrolyte is doubled, the value of molal elevation constant or Ebullioscopic constant ($K_b$) will be:

Select the correct alternative from the choices given: (i) The cell reaction is spontaneous or feasible when emf of the cell is: (1) negative (2) positive (3) zero (4) either positive or negative (ii) Which, among the following polymers, is a polyester: (1) melamine (2) bakelite (3) terylene (4) polythene (iii) The correct order of increasing acidic strength of the oxoacids of chlorine is: (1) $\text{HClO}_3 < \text{HClO}_4 < \text{HClO}_2 < \text{HCl}$ (2) $\text{HClO} < \text{HClO}_2 < \text{HClO}_3 < \text{HClO}_4$ (3) $\text{HClO}_2 < \text{HClO} < \text{HClO}_4 < \text{HClO}_3$ (4) $\text{HClO}_3 < \text{HClO}_4 < \text{HClO} < \text{HClO}_2$ (iv) A catalyst is a substance which: (1) changes the equilibrium constant of the reaction. (2) increases the equilibrium constant of the reaction. (3) supplies energy to the reaction. (4) shortens the time to reach equilibrium.

Match the following:

Answer the following questions: (i) (1) Which trivalent ion has maximum size in the Lanthanoid series i.e. Lanthanum ion ($\text{La}^{3+}$) to Lutetium ion ($\text{Lu}^{3+}$)? (at. no. of Lanthanum = 57 and Lutetium = 71) (2) Explain why $\text{Cu}^{2+}$ is paramagnetic but $\text{Cu}^+$ is diamagnetic. (at. no. of Cu = 29) (ii) When a coordination compound $\text{CoCl}_3 \cdot 6\text{NH}_3$ is mixed with $\text{AgNO}_3$, three moles of $\text{AgCl}$ are precipitated per mole of the compound. Write the structural formula and IUPAC name of the coordination compound. (iii) Calculate the boiling point of urea solution when $6\text{ g}$ of urea is dissolved in $200\text{ g}$ of water. ($K_b\text{ for water} = 0\cdot52\text{ K kg mol}^{-1}$, boiling point of pure water = $373\text{ K}$, mol. wt. of urea = $60$) (iv) Identify the compounds A, B, C and D in the given reaction: $\text{HC} \equiv \text{CH} \xrightarrow[\text{Hg}^{2+}/\text{H}_2\text{SO}_4]{\text{H}_2\text{O}} \text{A} \xrightarrow[\text{K}_2\text{Cr}_2\text{O}_7 + \text{H}_2\text{SO}_4]{[\text{O}]} \text{B} \xrightarrow{\text{Ca(OH)}_2} \text{C} \xrightarrow[\text{dry distillation}]{\text{heat}} \text{D}$

When $0\cdot4\text{ g}$ of oxalic acetic acid is dissolved in $40\text{ g}$ of benzene, the freezing point of the solution is lowered by $0\cdot45\text{ K}$. Calculate the degree of association of acetic acid. Acetic acid forms dimer when dissolved in benzene. ($K_f\text{ for benzene} = 5\cdot12\text{ K kg mol}^{-1}, \text{at. wt. C} = 12, \text{H} = 1, \text{O} = 16$)

A solution is prepared by dissolving $9\cdot25\text{ g}$ of non-volatile solute in $450\text{ ml}$ of water. It has an osmotic pressure of $350\text{ mm of Hg}$ at $27^\circ\text{C}$. Assuming the solute is non-electrolyte, determine its molecular mass. ($R = 0\cdot0821\text{ lit atm K}^{-1}\text{mol}^{-1}$)

Fill in the blanks by choosing the appropriate word/words from those given in the brackets: (more than, primary, cathode, Lucas reagent, two, four, less than, Grignard’s reagent, tertiary, anode, zero, equal to, three) (i) The elevation of boiling point of $0\cdot5\text{ M K}_2\text{SO}_4$ solution is ___________that of $0\cdot5\text{ M}$ urea solution. The elevation of boiling point of $0\cdot5\text{ M KCl}$ solution is __________ that of $0\cdot5\text{ M K}_2\text{SO}_4$ solution. (ii) A mixture of conc. $\text{HCl}$ and anhydrous $\text{ZnCl}_2$ is called __________ which shows maximum reactivity with _________ alcohol. (iii) In electrolytic refining the impure metal is made __________ while a thin sheet of pure metal is used as _________. (iv) When the concentration of a reactant of first order reaction is doubled, the rate of reaction becomes _________ times, but for a __________ order reaction, the rate of reaction remains the same.

An aqueous solution containing $12\cdot48\text{ g}$ of barium chloride ($\text{BaCl}_2$) in $1000\text{ g}$ of water, boils at $100\cdot0832^\circ\text{C}$. Calculate the degree of dissociation of barium chloride. ($K_b$ for water = $0\cdot52\text{ K kg mol}^{-1}$, at. wt. $\text{Ba} = 137$, $\text{Cl} = 35\cdot5$)

A solution containing $0\cdot5\text{ g}$ of $\text{KCl}$ dissolves in $100\text{ g}$ of water and freezes at $-0\cdot24^\circ\text{C}$. Calculate the degree of dissociation of the salt. ($K_f\text{ for water} = 1\cdot86^\circ\text{C}$).

The freezing point of a solution containing $5\cdot85\text{ g}$ of $\text{NaCl}$ in $100\text{ g}$ of water is $-3\cdot348^\circ\text{C}$. Calculate van’t Hoff factor ‘$i$’ for this solution. What will be the experimental molecular weight of $\text{NaCl}$? ($K_f$ for water = $1\cdot86\text{ K kg mol}^{-1}$, at. wt. $\text{Na} = 23$, $\text{Cl} = 35\cdot5$)

Calculate the amount of $\text{CaCl}_2$ (molar mass = $111\text{ g mol}^{-1}$) which must be added to $500\text{ g}$ of water to lower its freezing point by $2\text{ K}$, assuming $\text{CaCl}_2$ is completely dissociated. ($K_f\text{ for water} = 1\cdot86\text{ K kg mol}^{-1}$).