Advertisements
Advertisements
प्रश्न
What is meant by positive deviations from Raoult's law? Give an example. What is the sign of ∆mixH for positive deviation?
Advertisements
उत्तर
The solutions that do not obey Raoult’s law over the entire range of concentration are known as non-ideal solutions. They have vapour pressures either higher or lower than those predicted by Raoult’s law. If the vapour pressure is higher, then the solution is said to exhibit a positive deviation from Raoult’s law.
A mixture of ethanol and acetone is an example of a solution that shows a positive deviation from Raoult’s law.
In case of solutions showing positive deviations, absorption of heat takes place; that is, ΔmixH has a positive sign.
APPEARS IN
संबंधित प्रश्न
State Raoult’s law for the solution containing volatile components
Define azeotropes.
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.
What type of azeotrope is formed by positive deviation from Raoult’s law?
Some liquids on mixing form 'azeotropes'. What are 'azeotropes'?
Define Raoult’s law for the elevation of the boiling point of a solution.
The boiling point of an azeotropic mixture of water and ethanol is less than that of water and ethanol. The mixture shows ____________.
If the weight of the non-volatile solute urea (NH2–CO–NH2) is to be dissolved in 100 g of water, in order to decrease the vapour-pressure of water by 25%, then the weight of the solute will be ______ g.
