Calculate elevation of boiling point when 4 g of MgSO\(_4\) is dissolved in 100 g water.
(Molar mass = 120 g/mol), \( K_b = 0.52\ \text{K kg mol}^{-1} \), assume complete ionisation.
Show Hint
Solution and Explanation
Step 1: Molality \[ \text{Molality (m)} = \frac{\text{moles of solute}}{\text{mass of solvent in kg}} = \frac{4/120}{0.1} = \frac{1}{3} \] Step 2: van’t Hoff factor (i) MgSO\(_4\) dissociates completely → \( \text{Mg}^{2+} + \text{SO}_4^{2-} \Rightarrow i = 2 \) Step 3: Boiling point elevation \[ \Delta T_b = i \cdot K_b \cdot m = 2 \cdot 0.52 \cdot \frac{1}{3} = 0.346\ \text{K} \] \[ \boxed{\Delta T_b = 0.35\ \text{K (approx)}} \]
Top Questions on Colligative Properties
- Given below are two statements:
Statement (I): NaCl is added to the ice at \( 0^\circ C \), present in the ice cream box to prevent the melting of ice cream.
Statement (II): On addition of NaCl to ice at \( 0^\circ C \), there is a depression in freezing point.
In the light of the above statements, choose the correct answer from the options given below:- JEE Main - 2025
- Chemistry
- Colligative Properties
- Which of the following solutions will show highest freezing point depression?
- MHT CET - 2025
- Chemistry
- Colligative Properties
- 180 g of glucose, \(C_6H_{12}O_6\), is dissolved in 1 kg of water in a vessel. The temperature at which water boils at 1.013 bar is ______ (given, \(K_b\) for water is 0.52 K kg mol\(^{-1}\)). Boiling point for pure water is 373.15 K
- KCET - 2025
- Chemistry
- Colligative Properties
- HA $ (aq) \rightleftharpoons H^+ (aq) + A^- (aq) $ The freezing point depression of a 0.1 m aqueous solution of a monobasic weak acid HA is 0.20 °C. The dissociation constant for the acid is Given: $ K_f(H_2O) = 1.8 \, \text{K kg mol}^{-1} $, molality ≡ molarity
- JEE Main - 2025
- Chemistry
- Colligative Properties
Given below are two statements:
Statement (I): Molal depression constant $ k_f $ is given by $ \frac{M_1 R T_f}{\Delta S_{\text{fus}}} $, where symbols have their usual meaning.
Statement (II): $ k_f $ for benzene is less than the $ k_f $ for water.
In light of the above statements, choose the most appropriate answer from the options given below:- JEE Main - 2025
- Chemistry
- Colligative Properties
Questions Asked in CBSE Compartment XII exam
Solve the following LPP graphically: Maximize: \[ Z = 2x + 3y \] Subject to: \[ \begin{aligned} x + 4y &\leq 8 \quad \text{(1)} \\ 2x + 3y &\leq 12 \quad \text{(2)} \\ 3x + y &\leq 9 \quad \text{(3)} \\ x &\geq 0,\quad y \geq 0 \quad \text{(non-negativity constraints)} \end{aligned} \]
- CBSE CLASS XII - 2025
- CBSE Compartment XII - 2025
- Linear Programming
- For a chemical reaction A \(\rightarrow\) B, it was observed that the rate of reaction doubles when the concentration of A is increased four times. The order of the reaction is:
- CBSE Compartment XII - 2025
- Chemical Kinetics
- The thermal decomposition of an acid is a first-order reaction with a rate constant of \(2.3 \times 10^{-5}\ \text{s}^{-1}\) at a certain temperature. Calculate how long it will take for three-fourths of the initial quantity of acid to decompose. (\(\log 4 = 0.6021\), \(\log 2 = 0.3010\))
- CBSE Compartment XII - 2025
- Chemical Kinetics
- Assertion (A): Periodic abstinence is a method in which couples avoid coitus from day 10 to 17 of menstrual cycle.
Reason (R): Periodic abstinence has limited effectiveness because menstrual cycles are not always regular.- CBSE Compartment XII - 2025
- Reproductive Health
Four students of class XII are given a problem to solve independently. Their respective chances of solving the problem are: \[ \frac{1}{2},\quad \frac{1}{3},\quad \frac{2}{3},\quad \frac{1}{5} \] Find the probability that at most one of them will solve the problem.