Water solubility and concentration

Question 1

Wat is the shape of a water molecule and what type of bonds does it have

Answer 1

A water molecule has a bent V shape and contains 2 polar covalent bonds

Question 2

What are the forces that attract one water molecule to another

Answer 2

Relatively strong hydrogen bonds

Question 3

How many hydrogen bonds can a single water molecule make with other water molecules

Answer 3

4 hydrogen bonds in ice

Question 4

What gives water its high melting/boiling points

Answer 4

The strength of the hydrogen bonds, and
consequently the large amounts of energy required to disrupt the hydrogen bonds compared to other discrete molecules

Question 5

Identify and explain the patter of melting points down the group 16 hydrides

Answer 5

Except water, the melting point increases down the group 16 hydrides, due to increasing strength of dispersion forces

Question 6

Why is ice less dense than water

Answer 6

Due to its unique geometric arrangement of water molecules as a result of hydrogen bonding

Question 7

What is Heat capacity and what does it measure

Answer 7

Heat capacity is a measure of a substance’s capacity to absorb and store heat energy, and measures The quantity of energy in joules to increase the temperature of 1 gram of a substance by 1 degree

Question 8

Why is a heat capacity of water relatively high

Answer 8

The ability of the hydrogen bonds between water molecules to absorb and store heat energy

Question 9

Equation for the heat energy required to increase a mass of a substance by a particular temperature

Answer 9

q=mc ΔT

Question 10

what is q in q=mc ΔT

Answer 10

the heat energy

Question 11

what is m in q=mc ΔT

Answer 11

The mass in grams

Question 12

what is c in q=mc ΔT

Answer 12

C is the specific heat capacity

Question 13

what is ΔT in q=mc ΔT

Answer 13

The change in temperature

Question 14

What is latent heat

Answer 14

The energy or heat released or absorbed during a phase change of a material

Question 15

What type of process is the conversion of gas to liquid

Answer 15

Exothermic

Question 16

What type of process is the conversion of ice to water

Answer 16

Endothermic

Question 17

What is the latent heat of vaporisation of a substance

Answer 17

The heat energy needed to change 1 mole of the substance from a liquid to a gas at its boiling point

Question 18

What is the latent heat of fusion of a substance

Answer 18

The heat energy needed to change one mole of a substance from a solid to a liquid at its boiling point

Question 19

What equation is used to determine the heat energy requried to change the state of a substance

Answer 19

q= n x L

heat energy = amount(mol) x Latent heat

Question 20

Why does the relatively high latent heat of vaporisation of water have significance

Answer 20

For cooling of organisms and preservation of water supplies

Question 21

What effect do oceans have on global temperatures

Answer 21

The oceans have a buffering effect on global temperatures

Question 22

What is a precipitation reaction

Answer 22

A reaction between 2 soluble salts (aqueous salts) that produces an insoluble salt

Question 23

What is solubility

Answer 23

A measure of how much solute will dissolve in a given amount of solvent at a specified temperature

Question 24

What happens to the solubility of solids and gases are the temperature of a solution increases

Answer 24

The solubility of solids increase
the solubility of gases generally decrease

Question 25

What is the term given to a value that lies on the solubility curve

Answer 25

Saturated solution

Question 26

What is the term given to a value that lies under the solubility curve

Answer 26

Unsaturated solution

Question 27

What is the term given to a value that lies above the solubility curve

Answer 27

Supersaturated solution

Question 28

Why do gases become less soluble as temperatures increase

Answer 28

As the dispersion forces between gas and water are easily broken at hgih temperatures

Question 29

What is the term given to liquids that dissolve in a solvent | (e.g. H20)

Answer 29

Miscible

Question 30

What is the term given to liquids that don't dissolve in water | e.g. Oil

Answer 30

Form a layer and a called **immiscible**

Question 31

Factors that affect solubility

Answer 31

Hydrogen bonding Attraction between solute particles Temperature (for gases, pressure and temperature)

Question 32

What is concentration of a solution | solute and solution

Answer 32

The quantity of solute dissolved in a quantity of solution

Question 33

Molarity

Answer 33

The number of moles of solute per litre of solution

Question 34

Formula for molar concentration

Answer 34

c=n/V

Question 35

Symbol for Molar

Answer 35

M

Question 36

Alternative units of concentration

Answer 36

Grams per litre Parts per million Percentage mass for mass Percentage mass for volume

Question 37

What is ppm | formula

Answer 37

1mg per 1L

Question 38

Formula for Dilution

Answer 38

C2= (C1 x V1) / V2

Question 39

Conjugated base

Answer 39

An acid which has donated a proton (H+)

Question 40

Conjugated Acid

Answer 40

A base that has accepted a proton

Question 41

What is the Bronsted-Lowry theory

Answer 41

Describes *acids* as **proton donors** and *bases* are defined as **proton acceptors**

Question 42

Monoprotic

Answer 42

Acids that only have one proton to donate | e.g. HCl, HNO3

Question 43

Diprotic

Answer 43

Acids that have 2 protons to donate

Question 44

Triprotic

Answer 44

Acids that have 3 protons to donate

Question 45

Amphiprotic

Answer 45

Describes substances that can behave as either an acid or a base depending on what substance it is reacting with

Question 46

Why does water have a high latent heat

Answer 46

Large amounts of energy is needed to break the Hydrogen bonds so that the state can change

Question 47

What are the 3 key features of water

Answer 47

1) Has a relatively high melting point and boiling point 2)Has a high latent heat of fusion/vaporisation 3)Has a high specific heat capacity

Question 48

Why does ice expand when frozen

Answer 48

When water freezes each H20 molecule form 4 hydrogen bonds with 4 other h20 molecules, thus producing an open structure compound with liquid water where the molecules are sliding over each other.