Section 4-Inorganic Chemisty P2 Flashcards
Why do the elements in group 1 become more reactive as you go down the group?
- 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
Why does reactivity decrease as you go down group 7?
- 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
What metals are found in an uncombined state?
Unreactive metals such as Gold (sometimes silver)
Why are some metals found in an uncombined state?
- they are very unreactive
- so they don’t form compounds with other elements
- so they exist in an uncombined, raw state
What metals are found in ores?
(sometimes silver)
-more reactive metals than silver
copper, tin, iron, zinc, aluminium, magnesium, calcium, sodium, potassium
Define an ore:
A compound that contains enough of the metal to make it worthwhile extracting.
-there are limited amounts of them, they’re finite resources
What are the two main methods of extraction of metals from ores?
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
Reactivity series:
Potassium Sodium Calcium Magnesium Aluminium CARBON Zinc Iron Tin Copper Silver Gold
How is a reduction reaction used to extract metals less reactive than carbon from their ores?
- 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
What piece of equipment is used for the extraction of iron?
iron oxide is reduced in a blast furnace to make iron
How is electrolysis used to extract metals more reactive than carbon from their ores?
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
What common properties do iron, aluminium and copper have?
- 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
What are the uses of iron?
-wrought irons is almost completely pure iron, it’s malleable so its used for gates and railings
What is the main problem with iron?
That it corrodes easily
What are the uses of aluminium?
- 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
What are the uses of copper?
-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)
Why do pure metals not always have the properties needed?
The regular structure of metals often makes them too soft for use in everyday life
What is an alloy?
Alloys are made by adding other elements to the metal
Why are alloys stronger and harder forms of alloys?
- 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
What are alloys of iron called?
Steels
-they are made by adding small amounts of carbon and sometimes other metals to iron
What is brass made up of?
Brass is an alloy made up of, copper and zinc
What is bronze made up of?
Bronze is an alloy made of copper and tin
What is the property and use of low carbon steel?
low carbon steel (0.1%-0.3%)
property - easily shaped
use - car bodies
What is the property and use of high carbon steel?
high carbon steel(0.22%-2.5%)
property - very strong, brittle, inflexible
use - bridges
What is the property and use of stainless steel?
high carbon steel(0.22%-2.5%)
property - corrosion-resistant, hard
use - cutlery
What are three salt preparation methods?
Titration method
Excess base method
Precipitation method
What is a titration?
Titrations allow you to find out exactly how much acid is needed to neutralise a quantity of alkali (or vice versa)
What is a pipette?
A pipette is a piece of apparatus which only allows you to measure one volume of solution.
What is a burette?
Burettes measure different volumes and let you add the solution drop by drop
Describe a method for how you do a titration:
- 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
When calculating an average from titration experiments what results should you use?
Concordant values only(within 0.2 of each other)
What’s the equation linking volume, concentration and moles?
Concentration(mol/dm³) = moles / volume(dm³)
What’s the conversion between cm³ and dm³ ?
1 cm³ = 1000 dm³
What indicators do you use in titrations and why do you not use one type of indicator?
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
How can you make a dry sample of an insoluble salt?
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)
Describe a practical for making lead sulphate:
- 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
What methods can you use to make a soluble salt?
- using an acid and an insoluble base
- using an acid/alkali reaction
How can you use an acid/alkali (neutralisation) reaction to make a soluble salt? And why do you use this method?
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
Describe how you make a soluble salt by using a neutralisation reaction:
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)
