Studied by 0 peopleWhat is an acid?
A substance that forms aqueous solutions with a pH of less than 7
What is a base?
Any substance with a pH greater than 7
What is an alkali?
Alkalis are a sub-group of bases.
They are a base which dissolves in water to form a solution with a pH greater than 7.
What does ionise mean?
a substance splitting into its ions
What do acids do in aqueous solutions?
They ionise, producing H+ ions
What is a H+ ion? What does this mean for acids?
Just a proton as hydrogen only has 1 electron and it loses that to become an ion, meaning acids just produce protons in aqueous solutions.
what type of reaction is the ionisation of weak acids?
the ionisation of weak acids is a reversible reaction, meaning the reactant can react to form the product and the products can react to form the reactants, this sets up an equilibrium.
Where does the equilibrium in the ionisation of weak acids lie? What does this mean?
The equilibrium lies to the left, meaning that at equilibrium there are more particles of undissociated acid than molecules of dissociated acids, this is why weak acids are weak.
When would strong acids reach a low pH?
At most concentrations as all the acid particles dissociate fully, meaning lots of hydrogen ions being released.
What are some examples of bases?
Metal Oxides
Metal Hydroxides
Metal Carbonates
What is the reactivity series and a sentence to help remember it?
Please - Potassium
Send - Sodium
Little - Lithium
Charlies - Calcium
Monkeys, - Magnesium
And - Aluminium
Cheeky - Carbon
Zebras - Zinc
In - Iron
Heavy - Hydrogen
Lead - Lead
Cages - Copper
Securely - Silver
Guarded - Gold
What is another way you can determine how reactive metals are with an experiment?
You can use the same mass and surface of different metals and react them with an acid or water. The temperature change in the acid or water will tell you which metals are more reactive.
The greater the temperature change the more reactive that metal is.
What metals can react with water to form a metal hydroxide and hydrogen?
Only the most reactive metals like potassium sodium lithium and calcium.
Less reactive metals like zinc, iron and copper won't react at all
Magnesium will only react slightly.
What are metal oxides often?
Ores that metals need to be extracted from
What is a reduction reaction?
A reaction that separates a metal from its oxide, leaving a pure metal
What is reduction by carbon?
Reaction a metal oxide with carbon so that the carbon will take the oxygen from the metal forming carbon dioxide and leaving behind a pure metal.
What is an example of a Redox reaction?
displacement reactions
What is an electrode?
A solid that conducts electricity and is submerged in the electrolyte
What is the pH scale? Describe it.
the pH scale is a measure of how acidic or alkaline a solution is
1. pH 0 -> 6 are acids
2. pH 8 -> 14 are alkalis
3. A neutral substance has a pH of 7 (e.g pure water)
What is an indicator?
A dye that changes colour depending on whether it's above or below a certain pH
What is a wide range indicator? Give an Example.
An indicator that contains a mixture of dyes that means it gradually changes colour over a broad range of pH
For example universal indicator gives the colour each pH on the traditional pH scale
What is a pH probe? Why is it useful?
A pH probe is attached to a pH meter to measure pH electronically.
The pH probe gives a numerical reading on the meter, meaning its more accurate as it doesn't involve human guessing of shades
What is a reaction between an acid and a base called?
A neutralisation reaction
How to name a salt?
Salts have 2 part names.
The 1st part comes from the metal and the 2nd comes from the type of acid used.
E.g
HCl + NaOH --> NaCl + H2O
What is the pH of the products of a neutralisation reaction?
7 (neutral)
How can you tell when a neutralisation reaction is over and the substance has been neutralised?
Use an indicator to show the products are neutral (pH 7)
What is a strong acid?
An acid that is completely ionised in an aqueous solution, meaning all the acid particles dissociate to release H+ ions (this just means that all the acid particles split to form H+ ions.
What is a weak acid?
An acid that doesn't fully ionise in an aqueous solution, only a small portion of the acid particles dissociate to release H+ ions.
What is concentration in regards to acids?
How many acid particles there are in a certain volume of water
A concentrated acids contains...?
More acid particles compared to water particles in a unit of volume
What is pH a measure of?
concentration of hydrogen ions in a solution
As the concentration of hydrogen ions get higher what happens to the pH of a solution?
It gets lower
What does each decrease of 1 on the pH scale represent?
the hydrogen ions increasing by a factor of 10
When would weak acids reach a low pH?
Only at very high concentrations as so few of the acid particles dissociate so there aren't many hydrogen ions at low concentrations where there are less acid particles
How to make a soluble salt?
React acid with an insoluble base
E.g Metal hydroxide, metal oxide or metal carbonate
What is a sentence to help you remember the diatomic ions?
I
Have
No
Clever
Or
Bright
Friends
The ions which are always diatomic are I2, H2, N2, Cl2, O2, Br2, F2
When do ions become diatomic?
only after reacting
What is reactivity?
How easily a metal loses its outer electron(s) and forms positive ions
Why are carbon and hydrogen included in the reactivity series?
They are used as references to compare the metals against
How do the reactions of metals with cold dilute acid change as you go down the reactivity series?
The reactions become less violent and vigorous.
Metals like potassium, sodium, lithium and calcium all react explosive although potassium has the most violent reaction.
Metals like magnesium, zinc and iron react much less violently whilst copper won't with cold, dilute acid.
When an acid and metal react what visually determines the speed of reaction?
The rate at which the bubbles of hydrogen are given off.
How does magnesium react with cold dilute acid?
It reacts vigorously with cold dilute acid, producing loads of bubbles
How do zinc and iron react with cold dilute acid?
they react slowly and the rate at which they give off bubbles is slow
How can you increase the speed of zinc and iron reacting with cold dilute acid?
They would react more strongly if you heat the acid up
What is oxidation and reduction in terms of oxygen?
Oxidation is the gain of oxygen
E.g Magnesium reacting with oxygen to form Magnesium Oxide - Magnesium is oxidised
Reduction is a loss of oxygen
E.g Copper Oxide being broken down into copper and oxygen - copper is reduced
Why is metal oxide so common in the real world?
Since oxygen is so abundant in our atmosphere, most metal on earth will have come into contact with it at some point and in most cases if the metal has been left long enough it will have become oxidised
Which metals are an exception to this and don't become oxidised?
Very unreactive metals are found as pure metal as they aren't reactive enough to react with the oxygen around them and form metal oxides
What is the cheapest and easiest way to separate a metal from its oxide?
Reduction with carbon
What metals can be reduced with carbon?
Only those less reactive than metal (zinc, iron and copper)
How do metals more reactive than carbon get extracted?
Through electrolysis
What are downsides of electrolysis?
It requires lots of energy so it is very expensive
What are redox reactions?
reactions where REDuction and OXidation happen at the same time (REDOX)
What is oxidation and reduction in terms of electrons? What is a mnemonic to help remember this?
Oxidation is a loss of electrons
Reduction is a gain of electrons
OILRIG
Oxidation
Is
Loss
Reduction
Is
Gain
Why does reduction and oxidation happen at the same time?
If one substance loses electrons another substance has to gain them
What is a displacement reaction?
A More reactive metal displacing a less reactive one
What is an ionic equation?
A chemical equation that only shows the particles which take part in the reaction and change in some way
What are spectator ions?
Ions that do not take part in a reaction and therefore don't change in any way
What do half equations show?
The gain and loss of electrons
What is an electrolyte?
a liquid containing free-moving ions and can conduct electricity
Why must the electrodes in electrolysis be inert?
So they don't react with the electrolyte
Note
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