Pharmaceutics: Miscibility of Liquids

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Questions and Answers

What is the purpose of warming the tubes in a water bath in the miscibility temperature experiment?

To decrease the mutual solubility of phenol and water

To dissolve the phenol completely

To record the solution temperature (correct)

To increase the turbidity temperature

In the phenol-water system, what is the concentration of phenol in the phenolic layer?

63% phenol in water (correct)

50% phenol in water

24% phenol in water

11% phenol in water

What is the weight of the phenolic layer in the original mixture?

7.5 g

5 g

2.5 g (correct)

10 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 Signup and view all the answers

What is the weight of phenol in the aqueous layer?

0.825 g Signup and view all the answers

What is the new concentration of phenol in the phenolic layer after adding 0.1 mole of KCl?

59.4% phenol in water Signup and view all the answers

What is the weight of water in ph.Layer?

9 g Signup and view all the answers

At what temperature do the two-phase systems become one-phase systems?

At the temperatures given in the table Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

How much B needs to be added to produce a single phase at 10°C?

10g Signup and view all the answers

What is the percentage decrease in solubility of water when 0.1 mole of KCl is added?

10% Signup and view all the answers

What is the weight of the phenolic layer in 500 g of the mixture at 20°C?

326 g Signup and view all the answers

What is the concentration of phenol in the aqueous layer at 20°C?

8.4% Signup and view all the answers

What is the weight of phenol in the aqueous layer in 10 g of the previous mixture?

14.6 g Signup and view all the answers

What is the total weight of the original mixture at 30°C?

135 g Signup and view all the answers

What is the weight of the aqueous layer at equilibrium at 30°C?

105 g Signup and view all the answers

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.

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Description

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.