Chapter C5 Chemical Changes Flashcards
What are ores?
Rocks from which it is economical to extract metals that they contain
What does oxidised mean?
A substance that has had oxygen added to it
What are ores commonly chemically bonded to?
Oxygen from the air
Toe extract metals what must you do?
Reduce the metal oxide- have oxygen removed
Name the order of the reactivity series?
Potassium Sodium Lithium Calcium Magnesium Aluminium Carbon Zinc Iron Tin Lead Hydrogen Copper Silver Gold
What is the reactivity series?
A list of metals in order of their reactivity
Which metals fizz (give off hydrogen gas) when reacting with water?
Potassium
Sodium
Lithium
Calcium
What is fizzing?
Release of hydrogen gas
What happens when the most reactive metals react with water?
Fizz
Leave an alkaline solution of metal hydroxide
Which metals explode when reacting in dilute acid?
Potassium
Sodium
Lithium
Which metals have a very slow reaction with water?
Magnesium
Aluminium
Zinc
Iron
What requirement does aluminium have to meet before it reacts?
The oxygen must be removed
Which metals fizz when put in dilute acid?
Calcium Magnesium Aluminium Zinc Iron
What happens when C M A Z I react with dilute acid?
Fizz, release hydrogen gas
Form a salt
Which metals have a slight reaction with steam?
Tin lead
Which metals react slowly with warm acid?
Tin
Lead
Which metals do not react with water even when steam is present?
Copper
Silver
Gold
Which metals do not react with dilute acid?
Copper
Silver
Gold
What happens when a more reactive metal displaces a less reactive one?
Forms an aqueous solution of one of its salts
Give an example of a displacement equation
Magnesium + copper sulfate —>
Magnesium sulfate +copper
Define oxidation
Loss of electrons
Loss of oxygen
Define reduction
Gain of electrons
Where are metals found?
The earths crust
What is a metal ore?
When there is enough metal in a rock to make it worth extracting the metal
What are the three things that make it worth extracting a metal?
How easy it is to extract
How much metal the ore contains
The changing demands for a particular metal
What does carbon displace?
Less reactive metals from their oxides
Why use hydrogen to reduce oxide rather than carbon?
Carbon can result in the compound tungsten carbide
How are more reactive metals extracted from their ores if not reduction?
Electrolysis
When does a salt form?
When the hydrogenate in an acid is wholly or partially replaced by metal ions
How can you make salts?
Reacting metals more reactive than hydrogen with acid
Complete the equation
Metal + acid ——>
A salt + hydrogen
Why are alkali metals not reacted with acid?
Reaction is too vigorous
What is formed when a metal reacts with HCL?
Salt chlorides
What is formed when a metal reacts with sulphuric acid?
Sulfate salts
What is formed when a metal reacts with nitric acid?
Nitrate salts
Complete the equation
Mg + H^2SO^4—>
MgSO^4 + H^2
What are spectator ions?
ions that Do not change in the reaction
Complete the half equation
Mg——>
Mg^2+ + 2e-
If atoms lose electrons they have been…?
Oxidised
If an atom gains electrons, they have been…?
Reduced
What is a redox reaction?
Metal atoms donate electrons to hydrogen atoms displacing hydrogen as a gas and leaving metal ions the solution
What are bases?
Compounds that can neutralise acids
What happens when you react an acid with a base?
Salt and water is formed
What are salts made up of?
Positive metal ions and a negative ion from an acid
What charge are salts?
No charge
What happens when an acid and alkali react?
Neutralise, creating a salt and water
How do you collect a pure dry sample of salts?
Carry out the titration with the indicator to see how much acid reacts completely with the alkali
Run that volume of acid into the solution of alkali again, but without the indicator again
Then crystallise and dry out the crystals of salt from the reaction mixture
What is the equation for acid and a carbonate?
Acid + a carbonate —> a salt + water + carbon dioxide
Give an example of an aqueous solution?
Washing powder in a washing machine
What are soluble hydroxides called?
Alkalis
What ph is pure water?
Neutral 7
What do all acids release when reacting with water?
Excess H+ ions
What do alkalis produce when reacting with water?
Aqueous hydroxide solutions
What makes a solution alkaline?
Excess aqueous hydroxide ions
What is the sign for a hydroxide ion?
OH-
What are indicators?
Substances that change colour when added to acid or alkalis
What is the highest and lowest number on the PH scale?
0 and 14
What happens when you dilute a strong acid?
Eventually becomes harmless
What is the link between concentrated solutions and dilute solutions?
Concentrated solutions contain more of that solute than solutions of the same volume of a dilute solution
Give examples of weak acids
Ethanoic acid - strong acid is HCL
Citric acid- strong acid is nitric acid
Carbonic acid- strong acid is sulfuric acid
What are carboxylic acids?
Weak acids
What makes a solution acidic?
H+ ions
What is equilibrium?
The point in a reversible reaction at which the forward and backward rates of reaction are the same- this amounts remain constant
What is the difference in PH value of strong and weak acids?
Weak acids have a higher PH
What does decreasing the concentration of H+ ions mol/dm do to the PH level?
As the concentration per dm reduces by a factor of ten, the PH goes up by one
As the concentration of H+ ions increase by a factor of ten, what happens to the PH level?
Decreases by one unit