Section 4-Inorganic Chemisty P2

Question 1

Why do the elements in group 1 become more reactive as you go down the group?

Answer 1

• they loose electrons more easily as they go down the group because:
• > as you go down the group the outermost electron is in a shell that’s further away from the nucleus
• > this increased distance means the attraction between the outermost electron and the nucleus is weaker
• > as you go down the group the atoms get bigger so the outermost electron is a lot more easily lost so the element is more reactive

Question 2

Why does reactivity decrease as you go down group 7?

Answer 2

• Halogen only has to gain 1 electron to form a 1- ion with a stable electronic structure
• the easier it is for a halogen atom to attract an electron, the more reactive the halogen will be
• as you go down the group they become less reactive because it gets harder to attract the extra electron when its further away from the nuleus

Question 3

What metals are found in an uncombined state?

Answer 3

Unreactive metals such as Gold (sometimes silver)

Question 4

Why are some metals found in an uncombined state?

Answer 4

• they are very unreactive
• so they don’t form compounds with other elements
• so they exist in an uncombined, raw state

Question 5

What metals are found in ores?

Answer 5

(sometimes silver)
-more reactive metals than silver
copper, tin, iron, zinc, aluminium, magnesium, calcium, sodium, potassium

Question 6

Define an ore:

Answer 6

A compound that contains enough of the metal to make it worthwhile extracting.
-there are limited amounts of them, they’re finite resources

Question 7

What are the two main methods of extraction of metals from ores?

Answer 7

If a metal is more reactive than carbon:
-have to use electrolysis
If a metal is less reactive than carbon:
-use a reduction reaction using carbon

Question 8

Reactivity series:

Answer 8

Potassium
Sodium
Calcium
Magnesium
Aluminium
CARBON
Zinc
Iron
Tin
Copper
Silver
Gold

Question 9

How is a reduction reaction used to extract metals less reactive than carbon from their ores?

Answer 9

• by heating the ore with carbon monoxide
• this works because carbon is more reactive than these elements so it displaces the oxygen from the ore to form carbon dioxide

Question 10

What piece of equipment is used for the extraction of iron?

Answer 10

iron oxide is reduced in a blast furnace to make iron

Question 11

How is electrolysis used to extract metals more reactive than carbon from their ores?

Answer 11

The more reactive the metal is, the harder it is to extract from a compound (very reactive metals form very stable ores)
-electrolysis uses an electric current to separate the metal from other elements in the compound

Question 12

What common properties do iron, aluminium and copper have?

Answer 12

• dense and lustrous(shiny)
• have high melting points
• high tensile strength (strong, hard to break)
• malleable (can be hammered into different shapes)
• good conductors of electricity and heat

Question 13

What are the uses of iron?

Answer 13

-wrought irons is almost completely pure iron, it’s malleable so its used for gates and railings

Question 14

What is the main problem with iron?

Answer 14

That it corrodes easily

Question 15

What are the uses of aluminium?

Answer 15

• aluminium doesn’t corrode easily (it reacts quickly with the air to form a strong layer of aluminium oxide, which stops any further reactions from taking place), so it’s used for drinks cans
• aluminium is a lot less dense than iron, so it’s used in bike frames and aeroplanes

Question 16

What are the uses of copper?

Answer 16

-copper is an especially good conductor of heat and electricity, it’s used in electrical components and wiring, as well as heating systems (such as underfloor heating)

Question 17

Why do pure metals not always have the properties needed?

Answer 17

The regular structure of metals often makes them too soft for use in everyday life

Question 18

What is an alloy?

Answer 18

Alloys are made by adding other elements to the metal

Question 19

Why are alloys stronger and harder forms of alloys?

Answer 19

• because alloys contain more than one type of elements
• elements have different sized atoms
• these different sizes distort the layers so it’s harder for the layers to slide over each other

Question 20

What are alloys of iron called?

Answer 20

Steels

-they are made by adding small amounts of carbon and sometimes other metals to iron

Question 21

What is brass made up of?

Answer 21

Brass is an alloy made up of, copper and zinc

Question 22

What is bronze made up of?

Answer 22

Bronze is an alloy made of copper and tin

Question 23

What is the property and use of low carbon steel?

Answer 23

low carbon steel (0.1%-0.3%)
property - easily shaped
use - car bodies

Question 24

What is the property and use of high carbon steel?

Answer 24

high carbon steel(0.22%-2.5%)
property - very strong, brittle, inflexible
use - bridges

Question 25

What is the property and use of stainless steel?

Answer 25

high carbon steel(0.22%-2.5%)
property - corrosion-resistant, hard
use - cutlery

Question 26

What are three salt preparation methods?

Answer 26

Titration method
Excess base method
Precipitation method

Question 27

What is a titration?

Answer 27

Titrations allow you to find out exactly how much acid is needed to neutralise a quantity of alkali (or vice versa)

Question 28

What is a pipette?

Answer 28

A pipette is a piece of apparatus which only allows you to measure one volume of solution.

Question 29

What is a burette?

Answer 29

Burettes measure different volumes and let you add the solution drop by drop

Question 30

Describe a method for how you do a titration:

Answer 30

• use a pipette and a pipette filler to add 25cm³ of alkali to a conical flask, with three drops of phenolphthalein
• fill a burette with acid, below eye level
• use the burette to add acid to the alkali giving it a swirl each time, until the solution changes from pink to colourless
• record the volume of acid required to neutralise the alkali and repeat

Question 31

When calculating an average from titration experiments what results should you use?

Answer 31

Concordant values only(within 0.2 of each other)

Question 32

What’s the equation linking volume, concentration and moles?

Answer 32

Concentration(mol/dm³) = moles / volume(dm³)

Question 33

What’s the conversion between cm³ and dm³ ?

Answer 33

1 cm³ = 1000 dm³

Question 34

What indicators do you use in titrations and why do you not use one type of indicator?

Answer 34

Use: phenolphthalein and methyl orange
-don’t use universal indicator because it doesn’t have a definite colour change at one point it has a spectrum of colours

Question 35

How can you make a dry sample of an insoluble salt?

Answer 35

You can use a precipitation reaction
-you have to mix two soluble salts which will react together to form an insoluble salt (you know which ones to pick from the solubility rules)

Question 36

Describe a practical for making lead sulphate:

Answer 36

• add 1 spatula of lead nitrate to a test tube and dissolve it in deionised water, then get another test tube and do the same with magnesium sulphate
• pour both test tubes into a beaker and a precipitate of lead sulphate should form
• filter the precipitate off (using filter paper)
• rinse the contents of the filter paper with deionised water to make sure all of the magnesium nitrate is gone
• then dry the lead sulphate in a warm oven on fresh filter paper

Question 37

What methods can you use to make a soluble salt?

Answer 37

• using an acid and an insoluble base

- using an acid/alkali reaction

Question 38

How can you use an acid/alkali (neutralisation) reaction to make a soluble salt? And why do you use this method?

Answer 38

Need to perform a titration with an indicator
-because you can’t just add excess of alkali to acid, because since your salt is soluble it would be contaminated with excess alkali

Question 39

Describe how you make a soluble salt by using a neutralisation reaction:

Answer 39

perform a titration neutralising the acid and alkali and methyl orange or phenolphthalein as an indicator

• once it’s neutralised, record the amount of alkaline and acid need to neutralise each other
• then repeat the titration without an indicator (so it doesn’t contaminate the salt)
• slowly evaporate off some water and then the solution to crystallise, filter off the solid and dry it (warm oven)