Separation Techniques Flashcards
What are some methods to collect gases?
- Using a gas syringe
- Displacement through water
- Upward delivery
- Downward delivery
Is hydrogen soluble in water?
No
Is carbon dioxide soluble in water?
Slightly/No
Is oxygen soluble in water?
Very slightly/No
Is chlorine soluble in water?
Yes
Is hydrogen chloride soluble in water?
Very soluble
Is sulfur dioxide soluble in water?
Very soluble
Is ammonia soluble in water?
Extremely soluble
What are the drying agents available?
- Concentrated sulfuric acid
- Calcium oxide (quicklime)
- Fused calcium chloride
When should concentrated sulfuric acid be used as a drying agent?
Used for most acidic/neutral gases
Not suitable for alkali gases as it would react
When should calcium oxide be used as a drying agent?
Used to dry alkali gases
Not suitable for acidic gases that would react with it
When should fused calcium chloride be used as a drying agent?
Used to dry gases that cannot react with it such as CO2, oxygen, nitrogen, hydrogen chloride
Cannot be used with ammonia as it would react
What is the nature of carbon dioxide gas?
Acid/alkali/neutral
Acidic
What is the nature of hydrogen chlorine gas?
Acid/alkali/neutral
Acidic
What is the nature of chlorine gas?
Acid/alkali/neutral
Neutral
What is the nature of sulfur dioxide gas?
Acid/alkali/neutral
Acidic
What is the nature of ammonia gas?
Acid/alkali/neutral
Alkaline
How do you determine the purity of a substance?
- Check its boiling and melting points (should be fixed)
- Using chromatography
What is the effect of impurity on melting and boiling points
- Cause them to take place over a range of temperatures
- Decrease melting point, increase boiling point
What is the effect of pressure on boiling point?
As pressure increases, boiling point increases
What methods can you use to separate solid-solid mixtures?
- Magnetic attraction
- Sieving
- Sublimation
- Using suitable solvents
What methods can you use to separate insoluble solid-liquid mixtures?
- Filtration
What methods can you use to separate soluble solid-liquid mixtures?
- Evaporation to dryness
- Crystallisation
- Simple distillation
What methods can you use to separate liquid-liquid mixtures?
- Separating funnel
- Chromatography
- Fractional distillation
What is the procedure to carry out crystallisation?
- Solution is gently heated until saturation in an evaporating dish
- Cool the solution until crystals are formed
- After crystals are formed, filter and wash with small amounts of cold distilled water
- To obtain a dry pure crystal sample, dry between sheets of filter paper
What is the purpose of the boiling chips in a simple distillation set up?
To provide sites for formation of small bubbles (reducing bumping cause by big bubbles) or prevents flash boiling when dust particles agitate superheated liquids causing splatter
How to perform paper chromatography?
- Place solvent in container
- Draw a starting line about 1.5 cm away from the edge of paper with a pencil
- Apply a small spot of the chemicals to be analysed on the paper. Repeat application to concentrate the spot
- Carefully lower the paper into the solvent. Ensure the level of solvent is below the starting line
- When the solvent front nearly reaches the top of the chromatogram, remove the paper from the container and draw the solvent line with a pencil
How to calculate Rf (retention factor) value?
Rf value= X/Y
X= distance of spot from starting line
Y= distance from solvent front to starting line
