16.1 Practical Techniques in Organic Chemistry

Question 1

What is the name of this quickfit apparatus?

Answer 1

round-bottom flask/pear-shaped flask

Question 2

What is the name of this quickfit apparatus?

Answer 2

receiver

Question 3

What is the name of this quickfit apparatus?

Answer 3

screw-tap adaptor

Question 4

What is the name of this quickfit apparatus?

Answer 4

condenser

Question 5

What is the name of this quickfit apparatus?

Answer 5

Still head

Question 6

Why are some reactions carried out under reflux?

Answer 6

increase rate of reaction

without boiling off solvent, reactants or products

Question 7

Why is a heating mantle sometimes used during reflux instead of a bunsen burner?

Answer 7

to provide heat without a naked flame

prevents uncontrolled fires breaking out, should apparatus break with flammable liquids inside

Question 8

Is reflux carried out in an open or closed system?

Answer 8

open

due to heating, system must be open to accomodate increased air pressure & prevent explosion

Question 9

Why are anti-bumping granules used in reflux?

Answer 9

so the mixture boils smoothly.

without, large air bubbles would form, causing the apparatus to vibrate violently

Question 10

Reflux

How does water move through the condenser?

Answer 10

enters from bottom and leaves through top

(ensures outer jacket is always full)

Question 11

What is the purpose of distillation?

Answer 11

to separate a pure liquid from its impurities

Question 12

What is the purpose of the receiver in distillation?

Answer 12

to direct liquids from the liebig condenser into the conical flask

Question 13

What is the purpose of the condenser in distillation?

Answer 13

to condense vapours & direct them into the receiver

Question 14

What is the purpose of the still head in distillation?

Answer 14

to act as a junction between the liebig condenser & pear-shaped flask

Question 15

How does distillation work?

Answer 15

1. mixture of liquids in pear-shaped flask is heated using bunsen burner
2. liquid with lower boiling point evaporates, enters condenser.
3. condenses into liquid, travels down slanted condenser into receiver & into conical flask.
4. separates liquids using boiling point.

Question 16

What is a separating funnel used to separate?

Answer 16

2 liquids,

1 organic & 1 inorganic

Question 17

How can you differentiate between the organic & aqueous/inorganic layer in the separating funnel?

Answer 17

add water

the layer which gets bigger is the inorganic/aqueous layer

(because water is an inorganic solvent, it joins with the inorganic/aqueous layer)

Question 18

Outline the process by which 2 liquids can be separated using a separating funnel:

Answer 18

1. ensure tap of separating funnel is closed.
2. pour the mixture of liquids into the funnel.
3. place a stopper & invert the funnel, mixing the liquids.
4. allow them to settle to form 2 layers.
5. add water to identify the aqueous, inorganic layer.
6. place a conical flask under the funnel & remove the stopper.
7. open the tap and close it again when all of the lower layer has left the funnel.
8. place a new conical flask under the funnel and collect the other layer.

Question 19

How can you remove acid impurities in a liquid mixture of an inorganic & organic liquid?

Answer 19

add sodium carbonate

reacts to form salt + water + carbon dioxide

salt + water is removed with aqueous layer using separating funnel

Question 20

How can you remove traces of water left in an organic liquid?

Answer 20

add inorganic salt

acts as drying agent