18 Questions
What is the purpose of warming the tubes in a water bath in the miscibility temperature experiment?
To record the solution temperature
In the phenol-water system, what is the concentration of phenol in the phenolic layer?
63% phenol in water
What is the weight of the phenolic layer in the original mixture?
2.5 g
What is the effect of adding 0.1 mole of KCl to the phenol-water system?
It decreases the mutual solubility of phenol and water
What is the weight of phenol in the aqueous layer?
0.825 g
What is the new concentration of phenol in the phenolic layer after adding 0.1 mole of KCl?
59.4% phenol in water
What is the weight of water in ph.Layer?
9 g
At what temperature do the two-phase systems become one-phase systems?
At the temperatures given in the table
What happens when A is continually added to B at a temperature of 25°C?
A single liquid phase is observed up to 31% w/w A in B, and 2 liquid phases are observed above 31% w/w A in B
If a mixture containing A (20g) and B (30g) is prepared and allowed to come to equilibrium at 22°C, what are the compositions of the 2 phases?
30% w/w A and 70% w/w B; 80% w/w A and 20% w/w B
Ten grams of a mixture containing equal weights of A and B at 50°C are cooled to 10°C. At what temperature will the phase change be observed?
10°C
How much B needs to be added to produce a single phase at 10°C?
10g
What is the percentage decrease in solubility of water when 0.1 mole of KCl is added?
10%
What is the weight of the phenolic layer in 500 g of the mixture at 20°C?
326 g
What is the concentration of phenol in the aqueous layer at 20°C?
8.4%
What is the weight of phenol in the aqueous layer in 10 g of the previous mixture?
14.6 g
What is the total weight of the original mixture at 30°C?
135 g
What is the weight of the aqueous layer at equilibrium at 30°C?
105 g
Study Notes
Phase Changes in Immiscible Liquids
- A and B are partially miscible liquids, and their mixture forms two liquid phases below a certain temperature and one liquid phase above that temperature.
- The phase changes observed when A is continually added to B at a temperature of:
- 25°C: a single liquid phase up to 31% w/w A in B, 2 liquid phases from 31% A in B to 78% A in B, and a single phase is retained as A is further added.
- 45°C: a single phase exists for all combinations of A and B since the temperature is above the region of immiscibility.
Phase Compositions and Weights
- A mixture containing A (20g) and B (30g) prepared at 22°C:
- Compositions of the 2 phases: 30% w/w A and 70% w/w B; 80% w/w A and 20% w/w B.
- Weights of each phase: approximately 40g and 10g.
- Ten grams of a mixture containing equal weights of A and B at 50°C cooled to 10°C:
- Phase change observed at 34°C.
- At 10°C, 12.5g of B needs to be added to produce a single phase, and 87.5g of A needs to be added to produce a single phase.
Phenol-Water System
- A phenol-water system at 50°C with a total composition of 24% phenol in water:
- Respective concentrations of the 2 layers: 11% and 63% phenol in water.
- Weight of the aqueous layer: 7.5g.
- Weight of the phenolic layer: 2.5g.
- Weight of phenol in the aqueous layer: 0.825g.
- Weight of water in the aqueous layer: 6.675g.
- Weight of phenol in the phenolic layer: 1.575g.
- Weight of water in the phenolic layer: 0.925g.
Effect of KCl on the Phenol-Water System
- Addition of 0.1 mole of KCl decreases the mutual solubility of phenol and water by 10%:
- New points: 9.9 and 66.7.
- Weight of the aqueous layer: 7.52g.
- Weight of the phenolic layer: 2.48g.
Another Phenol-Water Mixture
- A phenol-water mixture at 20°C with a total composition of 50% phenol in water:
- Respective concentrations of the 2 layers: 8.4 and 72.2% phenol.
- Weight of the aqueous layer: 174g.
- Weight of the phenolic layer: 326g.
- Weight of phenol in the phenolic layer: 235.4g.
- Weight of phenol in the aqueous layer: 14.6g.
Yet Another Phenol-Water Mixture
- A mixture containing 21% by weight of phenol in water prepared at 30°C:
- Liquid phases that separate contain 7% and 70% by weight of phenol respectively.
- Total weight of the original mixture: 135g.
- Weight of the aqueous layer: 105g.
- Weight of the phenolic layer: 30g.
- Weight of water in the aqueous layer: not specified.
- Weight of water in the phenolic layer: not specified.
This quiz is about the miscibility of liquids, specifically the phenol-water system. It covers the preparation of tubes with increasing concentrations of phenol in water, recording temperatures, and determining the miscibility temperature. The quiz is suitable for pharmacy students.
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