Practical 5: distillation of a product from a reaction

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What are the reagents for partial oxidation of a primary alcohol?
K2Cr2O7 solution and dilute sulfuric acid
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What are the reagents for full oxidation of a primary alcohol?
Excess K2Cr2O7 solution and concentrated sulfuric acid
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What are the conditions for partial oxidation of a primary alcohol?
Limited amount of potassium dichromate, warm gently, distil out aldehyde as it forms.
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What are the conditions for full oxidation of a primary alcohol?
Excess potassium dichromate, heat under reflux (acid is distilled off after reaction has finished)
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What is observed when alcohols are oxidised by acidified K2Cr2O7?
Orange dichromate ion (Cr2O72-) is reduced to green chromate ion (Cr3+)
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Why is solid K2Cr2O7 hazardous and what precautions should be taken when handling it?
Highly toxic and carcinogenic (also an irritant). Wear gloves, avoid inhaling any dust.
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Why is a thermometer needed to measure the temperature of the vapours?
So that the distillate collected is the one with the approx. boiling point range of the desired product.
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Where should the bulb of the thermometer be positioned?
At the T - junction connecting the flask to the condenser.
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Why does the water go in the bottom of the condenser?
Against gravity - more efficient cooling (as coldest water meets coldest condensed product) and prevents backflow of water.
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Why are electric heaters often used to heat organic chemicals instead of bunsen burners?
Many organic chemicals are highly flammable and may set on fire with a naked flame.
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Why should the end of the condenser never be sealed?
Gases formed will cause an increase in pressure, which may cause the apparatus to explode.
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Why are anti - bumping granules used in heating?
Ensure even boiling by causing small bubbles to form rather than large ones.
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4 things to remember when drawing distillation apparatus
1) Don't draw lines between flask and condenser. 2) Don't seal top of condenser. 3) Outer tube for water must be sealed around top & bottom of condenser. 4) Two openings for water (in & out) on condenser that are not sealed.
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In lab fractional distillation, why should the thermometer be at or below the b.p. of the most volatile substance?
To prevent a mixture of substances from condensing into the flask.
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Other cards in this set

Card 2

Front

What are the reagents for full oxidation of a primary alcohol?

Back

Excess K2Cr2O7 solution and concentrated sulfuric acid

Card 3

Front

What are the conditions for partial oxidation of a primary alcohol?

Back

Preview of the front of card 3

Card 4

Front

What are the conditions for full oxidation of a primary alcohol?

Back

Preview of the front of card 4

Card 5

Front

What is observed when alcohols are oxidised by acidified K2Cr2O7?

Back

Preview of the front of card 5
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