Chapter 26: Alcohols

All the following "answers" are for your reference only!

The "best" answers are based on your actual experimental results!

 

Experiment 26.1: To make alcohol by fermentation

3.   To kill bacteria.

4.   The brewer's yeast may be killed if the temperature is too high.

5.   It turns milky.

6.   a)  When no more bubbles of gas are formed.

b)  Smells of alcohol.

7.   No. It contains too little alcohol and too much water.

8.   By distillation or fractional distillation. Refer to C26 P.6

9.   Yes.

Yes.

 

Experiment 26.2: Oxidation of ethanol

1.   a)  It changes from orange to green.

Dichromate ion is reduced to chromium(III) ion which is green.

b)  A pleasant "fruity" smell.

c)   CH₃CHO + H₂O

2.   a)  The purple colour changes to colourless.

Permanganate ion is reduced to manganese(II) ion.

b)  A pleasant "fruity" smell.

c)   CH₃CHO + H₂O

3.   a)  Reflux condenser.

b)  Any vapour is condensed and returned to the flask/ the mixture can be heated for a long time with little loss of vapour.

4.   Smell of vinegar.

5.   pH 2 to 3.

CH₃COOH + H₂O

 

Experiment 26.3: Preparation of an ester

3.   To condense the vapour back to a liquid so that the vapour cannot escape / as a condenser.

As a catalyst.

4.   No.

5.   a)  Yes. It has a sweet glue smell.

b)  To neutralize all the acids so that the smell of ester becomes more prominent.

6.   a)  Yes.

b)  CH₃CH₂OH + CH₃COOH ¾® CH₃COOCH₃CH₂ + H₂O

8.   No.

9.   ethyl ethanoate; catalyst.