Topic 2 - Inorganic Chemistry

Question 1

How do group 1 metals’ reactions with water provide evidence for them being in the same family of elements?

Answer 1

They all react with fizzing, floating of metal, moving around water, etc…

They all produce an alkaline metal hydroxide solution

These similarities provide evidence that they are all in the same group.

Question 2

How do the reactions of lithium, sodium and potassium with air and water provide evidence for the trend of reactivity as you go down group 1?

Answer 2

Lithium (Li)
Floats of water, fizzes
pH of metal hydroxide is alkaline

Sodium (Na)
Floats on water, melts into a ball, fizzes, and moves rapidly on the surface of water
pH is (more) alkaline

Potassium (K)
Burns with a lilac flame, melts, floats and moves rapidly on the surface of water
pH is (even more) alkaline

As we can see, as you move down the group, the elements are more reactive, which shows us that the trend of reactivity for group one is that they are more reactive the further down group one you go.

Question 3

How can the reaction of Lithium, Sodium and Potassium in water help us predict the reaction of Rubidium in water?

Answer 3

We know that reactivity increases as you go down the group, so we can predict that rubidium will react even more violently than potassium, and produce and even more alkaline metal hydroxide than potassium.

Question 4

Why are elements more reactive as you go down group 1?

Answer 4

Group one elements only need to lose one electron. This means that the atoms further down the group have more electron shells, and the outer shell of electrons (which they need to lose) is further from the nucleus and so has less attraction to the nucleus, making it easier to lose this electron as it is only weakly attracted to the nucleus.

Question 5

What are the group 1 metals also known as? Why?

Answer 5

The Alkali Metals, because they form alkali solutions when reacted with water

Question 6

What is group 7 also known as? Why?

Answer 6

The halogens, because they easily form salts, and in Greek ‘halogen’ means salt-former.

Question 7

What are the colours and state at room temperature of Fluorine, Chlorine, Bromine, and Iodine?

Answer 7

Fluorine - Light yellow/green gas at room temp
Chlorine - Green gas at room temperature
Bromine - Red/Orange liquid (easily vaporises to a red/orange gas)
Iodine - Grey solid (easily vaporises into a purple gas)

Question 8

What are common physical properties of the halogens?

Answer 8

They are diatomic molecules
Strong covalent bonds
Weak intermolecular forces
Low melting and boiling points
Poor conductors of heat and electricity

Question 9

How do melting and boiling points change as you go down group 7?

Answer 9

Melting and boiling point increases as you go down group 7.

Question 10

How does reactivity change in group 7?

Answer 10

Elements are more reactive as you go UP the group (fluorine more reactive than Chlorine, which is more reactive than bromine, etc…)

Question 11

How can displacement reactions show us the trend of reactivity in Group 7?

Answer 11

A more reactive halogen will displace a less reactive halogen, which shows us the order of reactivity by what displaces/reacts with what.

Question 12

Why does reactivity increase as you go up group 7?

Answer 12

The outer shell of electrons is closer to the nucleus. As halogens need to gain one electron, the closer the outer shell is to the nucleus, the stronger the force of attraction, and the easier it is for the atom to attract another electron and gain a full outer shell.

Question 13

How can metals be arranged into a reactivity series?

Answer 13

By testing their reactions with water and dilute hydrochloric acid, or sulfuric acid, we can deduce an order of reactivity based on how violent the reaction is.

Question 14

How can we use displacement reactions to order the reactivity series?

Answer 14

A metal will displace a less reactive metal from a salt or oxide, so we can use this to see what displaces what and then order a reactivity series.

Question 15

What is the order of reactivity? What is an acronym to help remember it?

Answer 15

Potassium - Please
Sodium - Stop
Lithium - Lamely
Calcium - Calling
Magnesium - Me
Aluminium - A
Carbon - Careless
Zinc - Zebra
Iron - Instead
Tin - Try
Lead - Learning
Hydrogen - How
Copper - Copper
Silver - Saves
Gold - Gold

Question 16

Under what conditions does iron rust?

Answer 16

When Water and Oxygen are present

Question 17

What 3 methods can be used to prevent the rusting of iron? How do these work?

Answer 17

Barrier method - Painting, oiling, greasing, electroplating. Provides an impermeable barrier between the iron and air (moisture, oxygen)

Sacrificial protection - Attaching a piece of a more reactive metal to the iron/steel. The more reactive metal oxidises in favour of the iron, so it is a ‘sacrifice’. The metal needs to be replaced once fully oxidised before the iron then starts to rust.

Galvanising - Involves both barrier and sacrificial protection. The iron/steel is plated in zinc, a more reactive metal than iron. The top layer of zinc oxidises in air, but no further corrosion takes place. If the zinc gets scratched, the lower exposed layer will then oxidise in favour of the iron beneath it, until the scratch is repaired.

Question 18

What are Oxidation and Reduction?

Answer 18

Oxidation
Is
Loss of electrons (Gain of oxygen)

Reduction
Is
Gain of electrons (Loss of oxygen)

Question 19

What is a redox reaction?

Answer 19

A reaction involving both oxidation and reduction.

Question 20

What is an oxidising/reducing agent?

Answer 20

Oxidising agent - The substance that is reduced, to allow the other substance to oxidise. (Takes electrons, gives oxygen)

Reducing agent - The substance that is oxidised, allowing the other substance to reduce. (Gives electrons, takes oxygen)

Question 21

How are most metals obtained?

Answer 21

They are extracted from their ores found in the Earth’s crust

Question 22

How are unreactive metals often found?

Answer 22

They are often found as native metals, unreacted/bonded to anything, just in their element form.

Question 23

How does the reactivity series play a role in the extraction method of a metal?

Answer 23

If a metal is less reactive than carbon, then it can be obtained by heating with carbon, as the carbon displaces the metal (e.g. Iron) from the compound (e.g. Iron Oxide).

If it is more reactive than carbon, then it needs to be obtained in another way, e.g. Aluminium is extracted by electrolysis.

Question 24

What are three uses of Aluminium, and the properties of aluminium that make it suitable?

Answer 24

Aircrafts & cans - Low density/Resists corrosion
Power cables - Conduct electricity/ductile
Pots and pans - Low density/ good conductor of heat

Question 25

What are three uses of copper, and the properties of copper that make it suitable?

Answer 25

Electrical wires - very good conductors of electricity and ductile Pots and Pans - Very good conductor of heat, malleable and very unreactive Water pipes - Unreactive and malleable

Question 26

What are two uses of iron, and the properties of iron that make it suitable?

Answer 26

Buildings - Strong Saucepans - Conducts heat/high melting point, and malleable.

Question 27

What is one use for Mild, High-carbon, and stainless steel, and the property of each steel that makes it suitable?

Answer 27

Mild steel - Up to 0.25% Carbon - Nails, car bodies, ship building, malleable High-carbon steel - 0.6-1.2% carbon - cutting tools, hard, brittle Stainless steel - Chromium and nickel - Cutlery, cooking utensils, as it is resistant to corrosion.

Question 28

What is an alloy?

Answer 28

A mixture of a metal and one or more elements, usually other metals or carbon.

Question 29

Why are alloys harder than pure metals?

Answer 29

They contain different types of metal atoms, so layers don't slide as well and it isn't malleable and is harder.

Question 30

What ion does an acid produce an excess of when dissolved in water? How about alkalies?

Answer 30

Acids produce an excess of hydrogen ions (H⁺) when dissolved in water. Alkalis produce an excess of hydroxide ions (OH⁻) when dissolved in water.

Question 31

What are the three solutions used to test a substance's spot on the pH scale?

Answer 31

Litmus Methyl Orange Phenolphthalein

Question 32

What colours will Litmus paper turn to indicate pH?

Answer 32

Red (pH 1-5), Purple (pH 5-9) and Dark purple (pH 9-14)

Question 33

What colours will Methyl orange turn to indicate pH?

Answer 33

Red (pH 1-5), Orange (pH 5-6) and Yellow (pH 7-14)

Question 34

What colours will Phenolphthalein turn to indicate pH?

Answer 34

Colourless (pH 1-10), Pink (pH 10-14)

Question 35

What range on the pH scale is acid, neutral or alkali?

Answer 35

1-3 Strongly acidic 3-6 Weakly acidic 7 Neutral 8-10 Weakly alkaline 11-14 Strongly alkaline

Question 36

How would you test an aqueous solution for pH value?

Answer 36

You would add universal indicator

Question 37

What is a base?

Answer 37

A base is a substance that can neutralise an acid, forming a salt and water. All alkalis are bases, but not all bases are alkalis.

Question 38

What can be used to neutralise an acid? How does it do this?

Answer 38

An alkali (or a base) can neutralise an acid by combining with the hydrogen ions in an acid, to neutralise it, because hydrogen ions are what makes an acid acidic.

Question 39

How would you carry out an acid-alkali titration?

Answer 39

This process is repeated a number of times. The first time it is done roughly to get a good approximation of how much alkali needs to be added. On subsequent attempts, the alkali is added very slowly when approaching the correct volume.

Question 40

What are the solubility rules?

Answer 40

1. All group 1 and ammonium compounds are soluble 2. All nitrates are soluble 3. Almost all sulphates are soluble apart from lead, barium and calcium 4. Almost all group 7 salts are soluble apart from silver, mercury and lead 5. Almost all carbonates and hydroxides are insoluble apart from group 1 and ammonium (rule 1)

Question 41

What are an acid and base in terms of proton transfer?

Answer 41

An acid is a proton donor A base is a proton acceptor A proton is the same as a hydrogen ion (H+). A good way to think about that is to realise that a hydrogen atom is just one proton and zero neutrons surrounded by only one electron. If that atom becomes an ion by the removal of the electron, then only one proton is left.

Question 42

What is a base? What is usually a base? What are alkalis in terms of bases?

Answer 42

A base is a substance that neutralises an acid by combining with the hydrogen ions in it to produce water. A base usually means a metal oxide, a metal hydroxide or ammonia. Alkalis are bases which are soluble in water.

Question 43

How would you prepare a pure, dry sample of a soluble salt, starting from an insoluble reactant? What would the steps be for the example of preparing copper sulphate crystals from copper oxide and sulphuric acid?

Answer 43

Using the excess method Example:

Question 44

What is the chemical test for? Hydrogen Oxygen Carbon Dioxide Ammonia Chlorine

Answer 44

Hydrogen - Put a lit splint near the gas, if hydrogen is present, there will be a squeaky pop. Oxygen - A glowing splint will relight if oxygen is present. Carbon Dioxide - Bubble through limewater, limewater turns cloudy white if carbon dioxide is present. Ammonia - Damp red litmus paper turns blue in the presence of ammonia. Chlorine - Damp blue litmus paper turns white (bleaches) in the presence of chlorine.

Question 45

How would you carry out a flame test?

Answer 45

A platinum or nichrome wire is dipped into concentrated hydrochloric acid to remove any impurities. The wire is dipped into the salt being tested, so some salt sticks to the end. The wire and salt are held in a roaring Bunsen burner flame. The colour the flame turns indicates the metal ions in the compound.

Question 46

What colour will: Li⁺ Na⁺ K⁺ Ca²⁺ Cu²⁺ Mg²⁺ Turn the flame in a flame test?

Answer 46

Li⁺ - Crimson red Na⁺ - Yellow/Orange K⁺ - Lilac Ca²⁺ - Brick red Cu²⁺ - Blue-green Mg²⁺ - No colour

Question 47

How would you test for NH₄⁺?

Answer 47

Add sodium hydroxide (NaOH), and heat If ammonium ions (NH₄⁺) are present, ammonia gas (NH₃) will form This will turn damp red litmus paper blue.

Question 48

How would you test for Copper (II) ions, Iron (II) ions and Iron (III) ions?

Answer 48

Add sodium hydroxide, and observe the colour:

Question 49

How would you test for Cl-, Br- and I-?

Answer 49

Add Nitric acid (HNO₃) to remove impurities Add silver nitrate (AgNO₃): If Chloride (Cl-) is present, a WHITE precipitate will form If Bromide (Br-) is present, a CREAM precipitate will form If Iodide (I-) is present, then a YELLOW precipitate will form.

Question 50

How would you test for Sulfate ions (SO₄²⁻)?

Answer 50

Add Hydrochloric acid (HCl) to remove impurities. Then add barium chloride solution (BaCl₂) If sulfate ions are present, a WHITE precipitate will form

Question 51

How would you test for carbonate ions (CO₃²⁻)?

Answer 51

Add Hydrochloric acid (HCl) If carbonate ions are present, fizzing will occur.

Question 52

How would you test for water?

Answer 52

Add anhydrous copper sulfate to the sample If water is present, then anhydrous copper sulfate will change from white to blue.

Question 53

How would you test to see if a sample of water is pure?

Answer 53

Test if it boils at 100⁰C and freezes at 0⁰C