Properties of Water

Question 1

what are some properties of water

Answer 1

1. Relatively high melting and boiling points
2. High specific heat capacity
3. High latent heat of fusion and high latent heat of
   vaporisation

Question 2

what is responsible for the properties of water

Answer 2

The polar O-H bond & the hydrogen bonding between
water molecules are responsible for the properties of
water.

Question 3

What are group 16 hydrides?

Answer 3

O, S, Se, Te and Po. Each
of these elements can bond with hydrogen to form
compounds known as hydrides.

Question 4

Why does the melting and boiling points of the other
group 16 hydrides increase as you move down the
group?

Answer 4

Dispersion forces increase in strength with increasing
mass. H2Po has a larger mass than H2S, hence has
stronger dispersion forces and high melting and boiling
points.

Question 5

water is the smallest group 16 hydride

Answer 5

Each water molecule has the potential to form 4 hydrogen bonds with surrounding water molecules. These hydrogen bonds are stronger than the
intermolecular forces found between other molecules.

Question 6

specific heat capacity

Answer 6

Amount of heat energy needed to increase the
temperature of a certain amount of substance by 1
oC

Question 7

how is specific heat capacity calculated

Answer 7

= SHC(J g−1°C−1) × mass (g) × temperature change (°C)
= SHC × mass (g) × ΔT (°C)
= mCΔT

Question 8

latent heat

Answer 8

Latent heat is the energy required to change a fixed amount of substance, usually 1 mole, from either a solid to a liquid or a liquid to a gas.

Question 9

Latent heat of fusion

Answer 9

6 kjmol-1– heat needed to change 1 mole of

the substance from solid to a liquid at melting point

Question 10

Latent heat of vaporisation

Answer 10

44.0 kjmol -1..heat needed to change 1
mole of the substance from liquid to a gas at boiling
point

Question 11

latent heat calculation

Answer 11

q = n × L
q = heat energy (kJ)
n = amount (mol)
L = latent heat value of fusion or vaporisation (kJ mol-1)

Question 12

homogenous solution

Answer 12

when a substance dissolves in a liquid

Question 13

dissolving

Answer 13

when the particles of the solvent and the solute form attractions with one another

Question 14

soluble

Answer 14

solution where the solute and solvent cannot be distinguished from eachother

Question 15

like dissolves like

Answer 15

rule where polar substances dissolves only polar substances and non-polar substances dissolves only non-polar substances can be used to predict if something will dissolve in a solvent.

Question 16

Why are the solvent properties of

water important?

Answer 16

• transport nutrients
• cleaning, drinking fluids
• fertiliser and medication

Question 17

Ways water acts as a solvent

Answer 17

2. Highly polar covalent molecules can ionise in water then form ion-dipole attractions with water
3. Ionic compounds can form ion-dipole attractions
   with water

Question 18

highly polar covalent molecules

Answer 18

h20 + HCl —-> H3O+ + Cl-

Question 19

ionic compound insoluble generalisations

Answer 19

 Ionic compounds that do not readily dissolve in water are insoluble in water.
 This means a greater amount of energy is needed to separate the ions from the lattice.
 Often increasing the temperature of water increases the solubility of ionic compounds.

Question 20

SNAPE

Answer 20

Sodium(Na+)
Nitrate(NO3-)
Ammonium(NH4+)
Potassium(K+)
Ethanoate (CH3COO-)

Question 21

what is a precipitation

Answer 21

 A precipitation reaction occurs if ions in a solution
combine to form an insoluble compound, this
substance is called the precipitate.

Question 22

what is solubility

Answer 22

The solubility of a substance refers to the maximum amount of that substance that can be dissolved in a given quantity of solvent at a certain temperature (g per
100g).

Question 23

crystallisation

Answer 23

When the temperature decreases and some solute comes out of solution to form crystals e.g. sugar is no longer dissolved in solution

Question 24

solubility of gases

Answer 24

temperature increases = solubilty decreases

temperature decreases = solubilty increases

Question 25

units of concentration (7)

Answer 25

Molarity – mol/L

2. Concentration in g/L
3. Concentration in mg/L or ppm
4. Concentration in ppb
5. Percentage by mass %(m/m)
6. Percentage by volume %(v/v)
7. Percentage mass/volume %(m/V)

Question 26

Molar concentration

Answer 26

c=n/v

Question 27

dilution

Answer 27

The process of adding more solvent to a solution
 This results in the solute particles becoming more
widely spaced (e.g. cordial and water).
 The concentration of solutes changes however the amount of solute remains the same.

Question 28

relationship between intial and final concentration and volume

Answer 28

c1V1=c2V2

Question 29

Gravimetric Analysis

Answer 29

Gravimetric analysis is a quantitative analysis of
substances based on mass.
 It can be used to determine:
 The water content of a substance (%)
 The empirical and molecular formula of a substance
 The amount of a particular ion in a substance by
forming a precipitate