Water and Solutions

Question 1

Define Latent Heat of Fusion

Answer 1

The energy required to convert one mole of a substance from a solid to a liquid at its melting point

Question 2

Define Latent Heat of Vaporisation

Answer 2

The energy required to convert one mole of a substance from a liquid to a gas at its boiling point

Question 3

Define Specific Heat Capacity

Answer 3

The energy required to raise the temperature of 1g of a substance by 1 degree Celsius

Question 4

Define Density

Answer 4

A measure of the mass of a substance per unit volume (eg g/L)

Question 5

Define Solubility

Answer 5

The degree to which a given solute will dissolve in a given solvent. Often expressed quantitatively with the units ‘g/100g solvent’

Question 6

Dissolution

Answer 6

The process of dissolving. Called dissociation for ionic compounds (as the ions ‘dis-associate’)

Question 7

Miscible

Answer 7

Refers to two liquids which can mix together readily (opposite = immiscible)

Question 8

Solvation

Answer 8

The process of water molecules surrounding a solute molecule or ion and bonding with it

Question 9

Ionisation

Answer 9

A reaction between a molecule (eg an acid) and water, resulting in the formation of two dissolved ions

Question 10

Suspension

Answer 10

Where a solid substance is dispersed in a solvent but not dissolved. The solid particles are distinguishable from the solvent particles. Suspensions usually settle over time and the solid can be separated by filtration.

Question 11

Colloid

Answer 11

A stable suspension, which will not settle over time

Question 12

Ion-dipole force

Answer 12

An attractive force between an ion and the oppositely charged pole of a polar molecule (such as water)

Question 13

Ionic Equation

Answer 13

A chemical equation in which the ‘spectator ions’ are omitted.

Question 14

ppm

Answer 14

A unit of concentration referring to ‘parts per million’: the concentration of a dissolved solute with the effective units of mg/L (in water) or micrograms per gram of solvent.

Question 15

%w/w

Answer 15

Concentration of a dissolved solute with the effective units of g/100g solvent

Question 16

%w/v

Answer 16

Concentration of a dissolved solute with the effective units of g/100mL solvent

Question 17

%v/v

Answer 17

Concentration of a dissolved liquid solute, with the effective units of mL/100mL solvent

Question 18

Solubility Curve

Answer 18

A graphical depiction of how the solute concentration required to form a saturated solution changes across a range of temperatures

Question 19

Saturated Solution

Answer 19

A solution in which the maximum amount of solute is dissolved, at that temperature

Question 20

Unsaturated Solution

Answer 20

A solution in which less than the maximum amount of solute is dissolved, at that temperature

Question 21

Supersaturated Solution

Answer 21

A solution in which more than the maximum amount of solute is dissolved, at that temperature. This is an unstable situation which can arise when a saturated solution cools, and is likely to result in crystallisation of some of the solute

Question 22

Crystallisation

Answer 22

Where a dissolved solute forms a solid due to it being in a supersaturated solution. This often arises due to the cooling of a saturated solution; the slower the solution cools the larger the crystals appear.