Separation and Solubility (Experiment 1)

Question 1

When describing the biphasic system observed in the separation funnel, what can be said about the composition of the dichloroindophenol aqueous layer and its density?

Answer 1

The aqueous layer in a separation funnel is an aqueous dye solution and its density are determined using the density of the dye (ie dichloroindophenol in part 1 and phenolphthalein in part 2)

Question 2

Part 1 of the experiment involved mixing an aqueous dye solution and dichloromethane in a separating funnel. Which statement correctly describes what was observed in the separating funnel?

Answer 2

A biphasic system was obtained (aqueous upper layer/dichloromethane lower layer) according to density.

Question 3

Was the acid (A) or base (B) form of the 2,6-dichloroindophenol dye indicator (part 1) most soluble in water and why?

Answer 3

The base form (B) of this dye indicator was more soluble in water. The base form is a polar ionic species so it interacts strongly with water molecules and dissolves readily to form an aqueous solution.

Question 4

What is a phenol group? Which form (A or B) of dichloroindophenol has one?

Answer 4

A phenol group is an HO group. Form B of dichloroindophenol has a phenol group.

Question 5

What is a conjugate base?

Answer 5

This is a substance formed when an acid loses a hydrogen ion.

Question 6

What is a conjugate acid?

Answer 6

A base substance which has acquired a hydrogen ion.

Question 7

What is meant when it is said that two liquids are miscible?

Answer 7

The liquids combine to form one homogenous mixture

Question 8

Which two liquids are miscible? What does their combination form?

Answer 8

Water and propan-1-ol combine to form a homogenous blue coloured solution because they are…

Question 9

In a biphasic system with a aqueous phenolphthalein dye solution layer and ethyl acetate layer, which is the upper layer?

Answer 9

The upper layer in this mixture is ethyl acetate because ethyl acetate is well-known to be less dense than water.

Question 10

How does the solubility of phenolphthalein vary according to pH?

Answer 10

Under acidic conditions, phenolphthalein is more soluble in the upper ethyl acetate layer.
Under basic conditions, phenolphthalein is more soluble in the lower aqueous layer.

Question 11

What are ester groups attached to rings, or rather cyclic esters, known as?

Answer 11

These groups are known as lactones in their cyclic form.

Question 12

What does the International Union of Pure and Applied Chemistry (IUPAC) define solubility as?

Answer 12

“As a proportion of a designated solute in a designated solvent”

Question 13

Which of the units below could be used to state the solubility of a substance?

a.
Molarity, M

b.
Molality, m

c.
Mole fraction, χ

d.
Normality, N

e.
Parts per million, ppm

Answer 13

All of the above!

Question 14

Define molarity (M).

Answer 14

This measure of concentration is the number of moles dissolved in a fixed volume of solvent (moles per litre, for example).

Question 15

Define molality (m).

Answer 15

This measure of concentration is the number of moles dissolved in a fixed mass of solvent (moles per kilogram).

Question 16

Define mole fraction.

Answer 16

This measure of concentration is the number of moles of solute divided by the total number of moles in the solution.

Question 17

Define normality (N).

Answer 17

This measure of concentration is the equivalents of solute per litre of solution.

Question 18

Define parts per million (ppm).

Answer 18

This unit is used to express low concentrations that would be inconveniently expressed using other units.