Advertisements
Advertisements
प्रश्न
Calculate the mass of a non-volatile solute (molar mass 40 g mol−1) which should be dissolved in 114 g octane to reduce its vapour pressure to 80%.
Advertisements
उत्तर
Given: Vapour pressure of pure solvent octane `(p_1^0)` = p
Vapour pressure of the solution (p1) = 80% of p = 0.80 p
Molar mass of solute (M2) = 40 g mol−1
Mass of solvent octane (w1) = 114 g
Molar mass of solvent octane (M1) = 114 g mol−1
According to Raoult’s Law for a non-volatile solute:
`(p_1^0 - p)/p_1^0 = n_2/(n_1 + n_2)`
Number of moles of solvent octane (n1) = `114/114`
= 1 mol
Number of moles of solute (n2) = `w_2/40`
Substitute the values into Raoult’s Law formula:
`(p - 0.80 p)/p = (w_2/40)/(1 + w_2/40)`
`(0.20 p)/p = (w_2/40)/((40 + w_2)/40)`
0.2 = `w_2/(40 + w_2)`
0.2 × (40 + w2) = w2
8 + 0.2 w2 = w2
8 = w2 − 0.2 w2
8 = 0.8 w2
w2 = `8/0.8`
= 10 g
संबंधित प्रश्न
What is meant by positive deviations from Raoult's law? Give an example. What is the sign of ∆mixH for positive deviation?
Define azeotropes.
What type of deviation is shown by a mixture of ethanol and acetone? Give reason.
The vapour pressures of pure liquids A and B are 450 and 700 mm Hg respectively, at 350 K. Find out the composition of the liquid mixture if the total vapour pressure is 600 mm Hg. Also, find the composition of the vapour phase.
The vapour pressure of water is 12.3 kPa at 300 K. Calculate vapour pressure of 1 molal solution of a non-volatile solute in it.
A solution containing 30 g of non-volatile solute exactly in 90 g of water has a vapour pressure of 2.8 kPa at 298 K. Further, 18 g of water is then added to the solution and the new vapour pressure becomes 2.9 kPa at 298 K. Calculate:
- molar mass of the solute.
- vapour pressure of water at 298 K.
Some liquids on mixing form 'azeotropes'. What are 'azeotropes'?
A solution containing 8.44 g of sucrose in 100 g of water has a vapour pressure 4.56 mm of Hg at 273 K. If the vapour pressure of pure water is 4.58 mm of Hg at the same temperature, calculate the molecular weight of sucrose.
Minimum boiling azeotrope is formed by the solution which showed
An aqueous solution of hydrochloric acid:
On the basis of information given below mark the correct option.
(A) In bromoethane and chloroethane mixture intermolecular interactions of A–A and B–B type are nearly same as A–B type interactions.
(B) In ethanol and acetone mixture A–A or B–B type intermolecular interactions are stronger than A–B type interactions.
(C) In chloroform and acetone mixture A–A or B–B type intermolecular interactions are weaker than A–B type interactions.
Using Raoult’s law explain how the total vapour pressure over the solution is related to mole fraction of components in the following solutions.
\[\ce{CHCl3(l) and CH2Cl2(l)}\]
Using Raoult’s law explain how the total vapour pressure over the solution is related to mole fraction of components in the following solutions.
\[\ce{NaCl(s) and H2O(l)}\]
Two liquids X and Y form an ideal solution. The mixture has a vapour pressure of 400 mm at 300 K when mixed in the molar ratio of 1 : 1 and a vapour pressure of 350 mm when mixed in the molar ratio of 1 : 2 at the same temperature. The vapour pressures of the two pure liquids X and Y respectively are ______.
A solution of a non-volatile solute in water freezes at −0.30°C. The vapour pressure of pure water at 298 K is 23.51 mm Hg and Kf for water is 1.86 degree/mol. The vapour pressure of rain solution at 298 K is ______ mm Hg.
The vapour pressure of pure liquid X and pure liquid Y at 25°C are 120 mm Hg and 160 mm Hg respectively. If equal moles of X and Y are mixed to form an ideal solution, calculate the vapour pressure of the solution.
