Section 1: Principles in Chemistry

Question 1

What are the three states of matter?

Answer 1

The three states of matter are a solid, liquid and gas.

Question 2

What is the difference in the particles between a solid and a liquid?

What is the difference in the particles between a liquid and a gas?

(forces, position, touching)

Answer 2

A solid has strong forces in between the particles keeping the particles in fixed positions. A liquidhas weak forceswhich allows them to move around but are usually packed closely together.

In a liquid, theparticles are packed closely together but are able to move around. There are weak forces between the particles. Gases are able to freely move around and expand.

Question 3

Name the 5 state changes and say what happens

Answer 3

Melting - solid to liquid
Boiling - liquid to gas
Condensing - gas to liquid
Freezing - liquid to solid
Sublimation - solid to gas

Question 4

Define diffusion

Answer 4

Diffusion is the movement of particles from a higer concentration to a lower concentration.

Question 5

Describe the experiment which demonstrates diffusion using ammonia and hydrochloric acid

Answer 5

Cotton wool soaked in aqueous ammonia is placed at one end of a glass tube and at the other end there’s a cotton wool soaked in hydrochloric acid. Eventually, a white ring made up of ammonium chloride will form closest to the hydrochloric soaked cotton wool. The ring is closest to the hydrochloric acid because the ammonia particles are lighter and smaller than they diffuse faster than the hydrochloric acid.

Question 6

Describe the structure of an atom

Answer 6

The nucleus is in the middle of an atom containing protons and neutrons. Electrons are found outside the nucleus in shells

Question 7

Name the the three particles found in an atom and state their mass and charge

Answer 7

A protons relative mass is 1 and its relative charge is +1.
A neutrons relative massis 1 and its relative charge is 0.
An electrons relative mass is 1/2000 and its relativecharge is -1.

Question 8

What does the mass number tell you?

What does the atomic number tell you?

Answer 8

The mass number tells me the total number of protons and neutrons in the atom.

The atomic number tells you the number of protons.

Question 9

When a small number of atoms are joined together by covalent bonds what do they form?

Answer 9

A molecule

Question 10

How are molecules held together?

Answer 10

They are held together by covalent bonds.

Question 11

What is an ion?

Answer 11

When electrons are added or removed from an atom it becomes charged making it an ion.

Question 12

How do you calculate the relative formula mass?

Ex. How would you find the Mr of MgCl2?

Ex. How would you find the Mr of C2H4(OH)2?

Answer 12

Add up the relative atomic massesof the atoms in the formula

Mg= 24 Cl= 35.5 MgCl2= Mg=24 + Cl2=(35.5x2)=95

C=12 H=1 0=16C2H4(OH)2= (16x2) + (1x4) + [(16+1) x 2] = 62

Question 13

How can you easily find the Ar of an element?

Answer 13

The mass number on the periodic table

Question 14

1 What is the mass of one mole of something

2 What do we measure moles in, what is the unit of moles?

3 How much is a mole?(Avagadro’s number of particles)

Answer 14

1 One mole of atoms or molecules of any substance will have a mass in grams equal to the molar mass

2 mol.

3 6.02x10 to the 23rd power

Question 15

How do you calculate moles from mass?

Answer 15

moles = mass ÷ molar mass

Question 16

What is the molar volume of gas (the volume 1 mole of gas will occupy)

Answer 16

24dm3or 24,000 cm3

Question 17

What is the equation for working out the number of moles of a gas?

Answer 17

moles = v (cm3) / 24000

Question 18

What is a covalent bond?

Answer 18

A covalent bond is formed when two non-metal atoms are combined together by sharing electrons. The positive nuclei of the atoms are attracted to the shared pair of electrons between them, it is a strong attraction

Question 19

Draw dot-cross diagrams for the following molecules:
Hydrogen - H2
Chlorine - Cl2
Hydrogen Chloride - HCl
Water - H2O
Methane - CH4
Ammonia - NH3
Oxygen - O2
Nitrogen - N2
Carbon Dioxide - CO2
Ethane - C2H6
Ethene - C2H4

Answer 19

Hydrogen atoms can each form one covalent bond. One pair of electrons is shared in a hydrogen molecule (H2)

Chlorine atoms can each form one covalent bond. One pair of electron is shared in a chlorine molecule (Cl2)

Hydrogen and chlorine atoms can each form one covalent bond. One pair of electrons are shared in a hydrogen chlorine atom

Hydrogen atoms can each form one bond, while oxygen atoms can each form two covalent bonds. The oxygen is in the middle with a bond to each hydrogen on either side

Hydrogen atoms can each from one covalent bond, while carbon can form four covalent bonds. A central carbon has four hydrogens bonded around it.

Hydrogen atoms can each form one covalent bond, while nitrogen can form three covalent bonds. A central nitrogen has three hydrogens bonded around it.

Oxygen atoms can each form two covalent bonds. The atoms share four electrons to form a double covalent bond between them

Nitrogen atoms can each from three covalet bonds. The atoms share six electrons to form a triple covalent bond between them.

Oxygen atoms can each form two covalent bonds, while carbon can form four covalent bonds.A central carbon forms a double to an oxygen atom on either side.

Hydrogen atoms can each form one covalent bonds, while carbon atoms can form four covaent bonds. Two carbons are bonded together and then 3 hydrogens are bonded to each carbon.

Hydrogen atoms can each form one covalent bond, while carbon can form four covalent bonds. The two carbons have a double bond between them and then another two hydrogens on each carbon

Question 20

Why do simple molecular substances have low boiling points?

Answer 20

They have low boiling points because they have weak forcesholding the molecules together which don’t require much energy to overcome

Question 21

Why do giant covalent structures have high melting points?

Answer 21

The have high melting points because they are in a lattice which has a lot of strong covalent bonds which need to be broken to melt the substance

Question 22

Draw diamond and graphite in terms of structure

Answer 22

Diamond- Draw one carbon with four others coming off it and continue on the other four
Graphite- Draw carbons in layers, 3 bonds between each atom, weak forces between layers

Question 23

For the reaction of magnesium and oxygen give the word equation and balanced symbol equation

Answer 23

Magnesium + Oxygen-> Magnesium Oxide

2Mg + O2 -> 2MgO

Question 24

What do these state symbols represnet?(s), (l), (g), (aq)

Answer 24

(s)-solid (l)-liquid (g)-gas (aq)-aqueous

Question 25

Can you balance this equation: C3H8 + O2 -> CO2 + H2O ? | `

Answer 25

C3H8 + 5O2 -> 3CO2 + 4H2O

Question 26

In some salts, water molecules are incorporated in the lattice. What is the water in the lattice called?

Answer 26

Water of crystallisation

Question 27

When a solid salt contains water of crystallisation, what is it?

Answer 27

Hydrated

Question 28

When a salt does not contain any water of crystallisation, what is it?

Answer 28

Anhydrous

Question 29

How can you calculate how much water of crystallisation salt contains?

Answer 29

If you know the mass of the hydrated and anhydrous salt, calculate the number of moles of water lost and anhydrous salt made. Work out the ratio of moles of anhydrous salt to mole of water, the final number must be rounded to a whole number.

Question 30

What does the empirical formulae work out?

Answer 30

The smallest whole number ratio of atoms in a compound

Question 31

How do you calculate the empirical formulae? 

Answer 31

1. Divide each mass or percentage by the relative atomic mas for the particular element. 2. Turn the numbers into a simple ratio by dividing them by the lowest number of those answers. 3. Adjust the ratio so all our whole numbers if necessary

Question 32

What is the molecular formula of a substance

Answer 32

The actual numbers of atoms of each element in a single molecule

Question 33

How do you calculate the molecular formulae?

Answer 33

The question will give you an empirical formula and a molecular mass. Find the mass of the empirical formula using the atomic masses of the element, divide the molecular mass by the mass of the empirical formula. The molecular formula is the empirical formula multiplied by this number.

Question 34

What is relative formula mass?

Answer 34

All of the atomic masses of a reactant or product added together. It is the same as molar mass.

Question 35

What is theoretical yield? 

Answer 35

The yield assuming 100% conversion of reactants to products

Question 36

How do you calculate the percentage yield?

Answer 36

By dividing the actual yield by the theoretical yeild and then multiplying the answer by 100. Note that it will always be somehwere between 0-100

Question 37

What happens to the charge of an atom when it: a. loses an electron b. gains an electron

Answer 37

a. becomes more positive | b. becomes more negative

Question 38

What is oxidation and reduction

Answer 38

Oxidation is the loss of electrons | Reduction is the gain of electrons

Question 39

Describe the changes when sodium and chlorine bond ionically

Answer 39

sodium loses an electron to become a + ion = Na+ | Chlorine gains the electron to become a - ion = Cl-

Question 40

Why do atoms form bonds?

Answer 40

To have a full outer shell to become stable

Question 41

``` What is the charge on the following ions (explain how they form)? Mg Br Na O Al N ```

Answer 41

Mg2+, magnesium has two electrons on it's outer shell so it loses two electrons to become Mg2+ Br-, bromine has seven electrons on it's outer shell so it gains one electron to become Br- Na+, sodium has only one electron on its's outer shell so only one electron is lost to become Na+ O2-, oxygen has six electrons on its outer shell so gains two electrons to become O2- Al3+, aluminium has three electrons on its outer shell so loses three to become 3+ N3-, nitrogen has five electrons on its outer shell so gains three to become 3-

Question 42

Using a dot and cross diagram explain the formation of Sodium Chloride

Answer 42

Sodium (x) has one electron on it's outer shell while Chlorine(.) has seven, this means that in the diagram chlorine will have an outer shell of 7 dots and 1 cross while the outer shell for Sodium will become 8 Xs

Question 43

What does the group number and period number of an element tell you?

Answer 43

The group number is the number of electrons on the outer shell. The period number is the number of shells

Question 44

Name the 4 different type of structures

Answer 44

Giant Ionic lattice Giant Metallic lattice Giant Covalent lattice Simple molecular lattice

Question 45

What kind of attraction is there between oppositely charged ions and how strong is it?

Answer 45

Electrostatic attraction, which is a very strong attraction

Question 46

What physical property do ionic compounds have as a result of the strong attraction?

Answer 46

A high boiling and melting point

Question 47

The structure of a metal is made out of?

Answer 47

Positive ions and a sea of delocalised electrons

Question 48

Name 5 properties of a metal

Answer 48

High melting/boiling point, shiny, good conductors of heat and electricity, malleable/ductile

Question 49

What is the attraction that holds metals together

Answer 49

The electrostatic attraction between positive ions and negative delocalised electrons

Question 50

Why do metals have high melting/boiling points?

Answer 50

Because their bonding is strong

Question 51

Why are alloys harder than metals

Answer 51

Because the lattice structure is disrupted so the atoms cannot easily move past each other

Question 52

Why do metals easily conduct electricity?

Answer 52

Because the delocalised electrons can move freely through the structure

Question 53

What is Electrolysis?

Answer 53

The decomposition of a compound by passing an electric current through it, often to form elements

Question 54

Negative ions _____ electrons at the positive electrode

Answer 54

Lose

Question 55

Positive ions _____ electrons at the negative electrode

Answer 55

Gain

Question 56

What are the rules for predicting the products of electrolysis?

Answer 56

Negative electrode - if reactive metal present in the solution hydrogen gas formed. If unreactive metal present then that is formed instead. Positive electrode - if a group 7 ion is present in the solution then that element is formed. If not oxygen gas is formed.

Question 57

``` What is produced at the anode and the cathode after the electrolysis of: Potassium bromide Silver Bromide Copper Sulphate Copper Chloride ```

Answer 57

``` Anode= Bromine, Cathode= Hydrogen Anode = bromine, cathode = silver Anode= copper, cathode = oxygen Anode= copper, cathode = chlorine ```

Question 58

What is the overall equation for the electrolysis of Potassium Nitrate and Potassium Sulphate solutions?

Answer 58

2H2O(l) -------> 2H2 (g) + O2 (g)

Question 59

What causes an increase in the amount of metal which is deposited at the negative electrode?

Answer 59

An increase in the current or an increase in the time the current flows for

Question 60

Why do covalent compounds not conduct electricity?

Answer 60

They have no free moving electrons or ions.

Question 61

Why can ionic compounds only conduct electricity when molten or in solution?

Answer 61

They can only conduct electricity when their ions are free to move. 

Question 62

Complete the following redox half equation: 2H+ + ___ e-   ----------> H2

Answer 62

2(e-)

Question 63

What happens at the electrodes during the purification of copper by electrolysis?

Answer 63

Impure copper at the anode is oxidised { Anode=  Cu -----> Cu2+    +    2e-   }    Pure copper is produced at the cathode    {  Cathode=    Cu2+      +      2e-   --------> Cu   }

Question 64

Define: element compound mixture

Answer 64

element - A substance containing only one type of atom compound - A substance containing more than one type of atom chemically combined mixture - A substance containing more than one type of atom not chemically combined

Question 65

Describe simple distillation

Answer 65

A process which separates a liquid with a lower boiling point from a solution

Question 66

Describe fractional distillation

Answer 66

A process which separates several liquids from a mixture with similar boiling points

Question 67

Describe filtration

Answer 67

A process which separates a mixture based on particle size with undissolved solids being unable to fit through the small holes in the filter

Question 68

Describe crystallisation

Answer 68

A process where a substance with a high boiling point is separated from a solution by allowing the solvent to boil or evaporate away

Question 69

Describe chromatography

Answer 69

A process where several substances in a mixture are separated by their solubility by allowing a solvent to absorb up a surface (e.g. paper) which the substance are on.

Question 70

Isotopes

Answer 70

Atoms of the same elements with the same chemical properties but different relative atomic mass. They have the same number of protons but a different number of neutrons

Question 71

Relative Atomic Mass (Ar)

Answer 71

The average mass of the atoms of an element | when compared to C-12

Question 72

What is the Periodic Table?

Answer 72

An arrangement of elements in order of atomic number, arranged into groups

Question 73

``` Give the electronic configuration for the following elements Hydrogen Lithium Nitrogen Fluorine Sodium Aluminium ```

Answer 73

``` H -1 Li - 2,1 N - 2,5 F - 2,7 Na - 2,8,1 Al - 2,8,3 ```

Question 74

Why is diamond very hard? Why does diamond not conduct electricity?

Answer 74

Because it has strong covalent bonds throughout the structure which are hard to break Diamond has no delocalised electrons

Question 75

Why is graphite used in lubricants? Why does graphite conduct electricity?

Answer 75

Because it has weak force between the layers, which can be easily broken. The layers are able to slide over each other. Because carbon atoms only form 3 bonds in graphite there is a left over delocalised electron which can move freely through the structure and conduct electricity.

Question 76

``` Define the following terms: Solute Solvent Solution Solubility Saturated ```

Answer 76

Solute - a substance that can dissolve in a solvent Solvent - a substance (normally a liquid) that a solute can dissolve into Solution - the mixture formed by a solute dissolving into a solvent Solubility - how well something can dissolve in a solvent Saturated - a solution that has the maximum amount of solute dissolved in the solvent, any additional solute added would remain undissolved

Question 77

The unit of solubility is often measured in g per 100g of solvent, what does this mean?

Answer 77

The amount in grams of a solute that can dissolve in 100 g of a specific solvent

Question 78

How is Rf value calculated in chromatography?

Answer 78

The distance travelled by the spot on the paper is divided by the distance the solvent travels is (the solvent front). The answer is always between 0 and 1.

Question 79

In electrolysis what is: A cation An anion

Answer 79

Cation - positive ion | Anion - negative ion

Question 80

``` What is the charge on the following ions: Ag Cu Fe Pb Zn OH NH4 CO3 NO3 SO4 ```

Answer 80

``` Ag+ Cu2+ Fe2+ or Fe3+ Pb2+ Zn2+ OH- NH4+ CO3 2- NO3 - SO4 2- ```

Question 81

Fullerenes (C60) as simple molecular forms of carbon where each forms 3 bonds to other carbon atoms. What you would expect in terms of melting point and electrical conductivity

Answer 81

Fullerenes would have low melting point as they are simple molecular with weak forces between the molecules. As they from only 3 bonds there is a last electron that is delocalised so they conduct electricity well.