Advertisements
Advertisements
Question
At 25 °C, a 0.1 molal solution of CH3COOH is 1.35 % dissociated in an aqueous solution. Calculate the freezing point and osmotic pressure of the solution assuming molality and molarity to be identical.
Advertisements
Solution
Given:
Molality of solution (m) = 0.1 m = 0.1 mol kg-1
Degree of dissociation (α) = 1.35% = 0.0135
Temperature = 25 °C = 25 °C + 273.15 = 298.15 K
Molarity of solution (M) = 0.1 M
To find:
1. Freezing point of solution
2. Osmotic pressure of solution
Formulae:
1. α = `("i" - 1)/("n" - 1)`
2. Δ Tf = i Kfm
3. π = i MRT
Calculation:
Using formula (i),
α = `("i" - 1)/("n" - 1) = "i" - 1` because n = 2
∴ i = 1 + α = 1 + 0.0135 = 1.0135
Now, using formula (ii),
Δ Tf = i Kfm = 1.0135 × 1.86 K kg mol-1 × 0.1 mol kg-1
= 0.189 K = 0.189 °C
Now, `triangle "T"_"f" = "T"_"f"^0 - "T"_"f"`
∴ `"T"_"f" = "T"_"f"^0 - "T"_"f" = 0^circ "C" - (0.189^circ "C")` = - 0.189 °C
Now, using formula (iii),
π = i MRT = 1.0135 × 0.1 mol dm-3 × 0.08205 dm3 atm K-1 mol-1 × 298.15 K = 2.48 atm
∴ The freezing point of the solution is – 0.189 °C
∴ The osmotic pressure of solution at 25 °C is 2.48 atm
APPEARS IN
RELATED QUESTIONS
Answer the following in one or two sentences.
What is van’t Hoff factor?
Answer the following in one or two sentences.
Which of the following solution will have higher freezing point depression and why?
i. 0.1 m NaCl
ii. 0.05 m Al2(SO4)3
Derive the relationship between the degree of dissociation of an electrolyte and van’t Hoff factor.
A 0.15 m aqueous solution of KCl freezes at - 0.510 °C. Calculate i and osmotic pressure at 0 °C. Assume the volume of solution equal to that of water.
At T (K), the molar ionic conductivities of NH; and OH− at infinite dilution are 72 and 198 S cm2 mol−1 respectively. The molar conductivity of 0.01 M NH4OH solution at the same temperature is found to be 9 S cm2 mol−1. The percentage dissociation of NH4OH at this concentration is ____________.
Calculate van't Hoff-factor for 0.2 m aqueous solution of KCl which freezes at - 0.680°C. (Kf = 1.86 K kg mol-1).
Osmotic pressure of a urea solution at 10°C is 500 mm Hg. Osmotic pressure of the solution become 105.3 mm Hg, when it is diluted and temperature is raised to 25°C. The extent of dilution is ____________.
0.6 g of a solute is dissolved in 0.1 L of a solvent which develops an osmotic pressure of 1.23 atm at 27°C. The molecular mass of the solute is ______.
Relationship between van't Hoff's factor (i) and degree of dissociation (α) is ______.
The osmotic pressure of a solution containing 10 g of cane sugar dissolved in 100 mL of water at 70°C is ____________.
Which of the following equation is correct to determine osmotic pressure using van't Hoff equation?
Why is observed molar mass of acetic acid in benzene is greater than actual molar mass?
Which of the following equations is NOT correct for van't Hoff factor?
Solution of 'A' containing 1.73 g of it in 100 cm3 of water is found to be isotonic with a 3.42% (w/v) solution of sucrose. The molecular weight of A is ______. (At. mass C = 12, H = 1, 0 = 16)
0.01 m aqueous formic acid solution freezes at – 0.021°C. Calculate its degree of dissociation, Kf = 1.86 K kg mol–1.
The equation that represent general van't Hoff equation is ______.
Calculate the van't Hoff factor assuming the complete dissociation of NaBr in its aqueous solution.
Calculate ΔTb and boiling point of 0.05 m aqueous solution of glucose. (Given: Kb = 0.52 K m−1).
The value of van't Hoff factor will be minimum for ______.
For 1 molal aqueous solution of the following compounds, which one will show the highest freezing point?
The depression in freezing point of 0.2 m aqueous solution of an electrolyte is 0.7 K. Calculate its percent degree of dissociation. [Kf for water = 1.86 K kg mol-1; n = 2]
