C2.2 Ionic compounds and analysis Flashcards
What is an ion?
An atom with a positive or negative charge
How do atoms become ions?
They lose or gain electrons in chemical reactions
What are cations?
Positively charged ions
How do atoms become cations?
They lose electrons
What are anions?
Negatively charged ions
How do atoms become anions?
They gain electrons
Is a metal ion a cation or an anion?
Cation
Is a non-metal ion a cation or an anion?
Anion
Why do anions gain electrons?
To complete their outer shells
Do oppositely charged ions attract or repel?
Attract
What are ionic bonds?
Strong electrostatic forces between oppositely charged atoms
What is the charge of an ionic compound?
0, neutral
Why is an ionic compound neutral?
There are equal numbers of positive and negative charges
What are compound ions?
Ions that contain more than one element
What is a lattice structure?
When something is arranged in a regular way
When can ionic substances conduct electricity?
When they are molten or in aqueous solution
What two conditions must be met for a substance to conduct electricity?
It must contain charged particles and those particles must be free to move
Why can’t ions conduct electricity when they’re solid?
The ions are held in fixed positions because they’re in a lattice structure so they can only vibrate
What is the melting point?
The temperature at which a substance turns from a solid to a liquid
What is the boiling point?
The temperature at which a substance turns from a liquid to a gas at its fastest possible rate
Do ionic substances have high or low melting and boiling points?
High
Why do ionic compounds have high melting and boiling points?
Ionic bonds are very strong so a lot of energy is needed to break them
What does soluble mean?
A substance that dissolves well in a liquid
What does insoluble mean?
A substance that doesn’t dissolve in a liquid at all
What is a salt?
A substance that can be made by reacting an acid and an alkali
What is a precipitate?
An insoluble product of a reaction
What is a precipitation reaction?
A reaction in which an insoluble solid is produced from two soluble substances
How can you separate the precipitate from unreacted ions?
- through filtration
- then washing it on the filter paper
- then drying it in a warm oven
Are chlorides, nitrates and common potassium salts soluble or insoluble?
Soluble
Are hydroxides and lead salts soluble or insoluble?
Insoluble
What is a barium meal?
A drink containing barium sulphate used for X-rays
Why is barium sulphate used in X-rays?
It shows up opaque on X-rays because X-rays don’t pass through but get absorbed
Why is barium sulphate safe to swallow while most barium salts are toxic?
Barium sulphate is insoluble which means it doesn’t get absorbed into the blood
Why are flame tests used?
To help identify elements
What colour does sodium go during a flame test?
Yellow
What colour does potassium go during a flame test?
Lilac
What colour does calcium go during a flame test?
Red
What colour does copper(||) go during a flame test?
Green-blue
What is a spectroscopy?
The analysis of light on a spectrum using flame tests
How do you do a spectroscopy?
You study the light given off flame tests on mineral water. Then a prism is used to separate the colours
How were caesium and rubidium discovered?
Using a spectroscopy
How do you identify aqueous chloride ions?
- you add a few drops of dilute nitric acid to the sample solution which is shaken
- you then add a few drops of silver nitrate solution
- if a white precipitate of silver chloride forms there are chloride ions
How do you identify aqueous sulphate ions?
- you add a few drops of dilute hydrochloric acid to the sample solution which is shaken
- you then add a few drops of barium chloride solution
- if a white solution of barium sulphate forms the solution contains sulphate ions
How do you test for carbonate ions?
- you add acid to the substance so that gas is given off
- if the gas turns limewater milky then it is carbon dioxide
