Chemical Changed Flashcards
What is produced when a metal reacts with oxygen?
Metal oxide
What is oxidation?
Gain of oxygen
What is reduction?
Loss of oxygen
What is the reactivity series?
Metals arranged in order of their reactivity
How are metals ordered in the reactivity series?
The tendency of the metal to lose electrons and form positive ions
What is the order of the metals in reactivity series?
Potassium, sodium, lithium, magnesium, zinc, iron and copper
What experiments can be done to put metals in their reactivity series?
How they react with water and acids
Why would you not use acids to predict the reactivity of sodium and potassium?
As very reactive would be too dangerous
What are the products when a metal reacts with water?
Metal hydroxide and hydrogen
What are the products when a metal reacts with an acid?
Salt and hydrogen
What two non-metals are placed in the reactivity series?
Carbon and hydrogen
What is displacement reaction?
When a more reactive metal can displace a less reactive metal from a compound
How are unreactive (native) metals found in the earth?
As the metal itself
How are metals which are less reactive than carbon extracted from their oxides?
Using carbon
How are metals which are more reactive than carbon extracted from their oxides?
By electrolysis
What is oxidation in terms of electron (HT only)?
Loss of electrons
What is reduction in terms of electrons (HT only)?
Gain of electrons
What is redox reaction (HT only)?
Reduction and oxidation occurring
What is an oxidising agent?
A substance that causes another chemical to gain oxygen
What is a reducing agent?
A substance that causes another chemical to lose oxygen
What is the pH scale?
A scale of how acidic or alkaline a substance is.
What pH are acids?
Less than 7 (red/orange/yellow).
What pH are alkalis?
More than 7 (blue/purple).
What pH is neutral?
7 (green).
What can be used to measure pH?
Universal indicator or a pH probe.
What is a base?
A metal oxide.
What is an alkali?
A metal hydroxide, a base that is soluble (e.g. Na2O can dissolve to make NaOH).
What ion is in all acids?
H⁺ (hydrogen ion).
What ion is in all alkalis?
OH⁻ (hydroxide ions).
What type of reaction occurs between an acid and an alkali?
Neutralisation.
What is the general equation for neutralisation?
Acid + alkali → salt + water.
What is the ionic equation for neutralisation?
H⁺ (aq) + OH⁻ → H₂O.
What is made when an acid reacts with an alkali?
Salt and water.
What is made when a metal carbonate reacts with an acid?
Salt, water and carbon dioxide.
What is the formula for hydrochloric acid?
HCl.
What is the formula of sulphuric acid?
H₂SO₄.
What is the formula of nitric acid?
HNO₃.
What salt is made from hydrochloric acid?
Chloride.
What salt is made from sulphuric acid?
Sulphate.
What salt is made from nitric acid?
Nitrate.
How can you make a soluble salt?
By reacting a metal, metal hydroxide or metal oxide with an acid.
How can you make sure all of the acid used up when making a soluble salt?
Keep adding the metal etc. until no more reacts.
How can you remove the metal/metal oxide or metal hydroxide that hasn’t reacted when making a soluble salt?
Filter it off.
What is the process called when a solid salt is obtained from a salt solution?
Crystallisation.
What is a strong acid?
An acid that is completely ionised in aqueous solution (e.g. Hydrochloric, sulphuric and nitric).
What is a weak acid?
An acid that is only partially ionised in aqueous solution (e.g. Ethanoic, citric, carbonic).
What does a change in pH of one unit mean?
The hydrogen ion concentration of the solution has changed by a factor of 10.
What is electrolysis?
The breakdown of a compound back to its elements using electricity.
What must compounds be for electrolysis to work?
Molten (melted) or in solution.
Why must a compound be melted or in solution for electrolysis to work?
So that the ions are free to move.
What is a solution called that can conduct electricity?
Electrolyte.
What are positive ions called?
Cations.
What are negative ions called?
Anions.
What is the positive electrode called?
Anode.
What is the negative electrode called?
Cathode.
What is the pH scale?
A scale of how acidic or alkaline a substance is.
What pH are acids?
Less than 7 (red/orange/yellow).
What pH are alkalis?
More than 7 (blue/purple).
What pH is neutral?
7 (green).
What can be used to measure pH?
Universal indicator or a pH probe.
What is a base?
A metal oxide.
What is an alkali?
A metal hydroxide, a base that is soluble (e.g. Na2O can dissolve to make NaOH).
What ion is in all acids?
H⁺ (hydrogen ion).
What ion is in all alkalis?
OH⁻ (hydroxide ions).
What type of reaction occurs between an acid and an alkali?
Neutralisation.
What is the general equation for neutralisation?
Acid + alkali → salt + water.
What is the ionic equation for neutralisation?
H⁺ (aq) + OH⁻ → H₂O.
What is made when an acid reacts with an alkali?
Salt and water.
What is made when a metal carbonate reacts with an acid?
Salt, water and carbon dioxide.
What is the formula for hydrochloric acid?
HCl.
What is the formula of sulphuric acid?
H₂SO₄.
What is the formula of nitric acid?
HNO₃.
What salt is made from hydrochloric acid?
Chloride.
What salt is made from sulphuric acid?
Sulphate.
What salt is made from nitric acid?
Nitrate.
How can you make a soluble salt?
By reacting a metal, metal hydroxide or metal oxide with an acid.
How can you make sure all of the acid used up when making a soluble salt?
Keep adding the metal etc. until no more reacts.
How can you remove the metal/metal oxide or metal hydroxide that hasn’t reacted when making a soluble salt?
Filter it off.
What is the process called when a solid salt is obtained from a salt solution?
Crystallisation.
What is a strong acid?
An acid that is completely ionised in aqueous solution (e.g. Hydrochloric, sulphuric and nitric).
What is a weak acid?
An acid that is only partially ionised in aqueous solution (e.g. Ethanoic, citric, carbonic).
What does a change in pH of one unit mean?
The hydrogen ion concentration of the solution has changed by a factor of 10.
What is electrolysis?
The breakdown of a compound back to its elements using electricity.
What must compounds be for electrolysis to work?
Molten (melted) or in solution.
Why must a compound be melted or in solution for electrolysis to work?
So that the ions are free to move.
What is a solution called that can conduct electricity?
Electrolyte.
What are positive ions called?
Cations.
What are negative ions called?
Anions.
What is the positive electrode called?
Anode.
What is the negative electrode called?
Cathode.
What does PANIC stand for?
Positive anode, negative is the cathode
What are electrodes normally made from?
Graphite (carbon) as it conducts electricity
What do opposite charges do?
Attract
What electrode do positive ions (cations) move to?
Negative (cathode)
What electrode do negative ions (anions) move to?
Positive (anode)
What electrode do metals form at?
Cathode (as metals form positive ions)
What electrode do non-metals form at?
Anode (as non-metals form negative ions)
What electrode does hydrogen form at?
Cathode as hydrogen ions are positive
What is formed at each electrode for molten potassium bromide?
Potassium at the negative electrode (cathode), bromine at the positive electrode (anode)
What happens to positive ions at the cathode in terms of electrons (HT only)?
Gain electrons (reduction)
What happens to negative ions at the anode in terms of electrons (HT only)?
Lose electrons (oxidation)
What does OILRIG stand for (HT only)?
Oxidation is loss reduction is gain of electrons
Why is extracting a metal using electrolysis expensive?
Uses large amounts of energy to melt the compound and for the electrical current
What is the ore aluminium is extracted from?
Aluminium oxide (bauxite)
What is added to aluminium oxide when it is extracted using electrolysis?
Cryolite
Why is cryolite added to aluminium oxide when it is extracted using electrolysis?
To lower the melting point so reduces energy costs
What are the electrodes made from in the electrolysis of aluminium oxide?
Carbon (graphite)
Why do the carbon electrodes need replacing often in the electrolysis of aluminium oxide?
The oxygen produced reacts with the carbon electrodes to make carbon dioxide so they wear away
What is an equation to show how the carbon electrodes wear away in the electrolysis of aluminium oxide?
Carbon + oxygen → carbon dioxide
(C + O₂ → CO₂)
What electrode does aluminium form at during electrolysis?
Negative (cathode) as aluminium is positively charged
What electrode does oxygen form at during electrolysis of aluminium oxide?
Positive (anode) as oxide is negatively charged
What is the half equation for the formation of Aluminium (HT only)?
Al³⁺ + 3e⁻ → Al
(reduction is gained electrons)
What is the half equation for the formation of oxygen (HT only)?
2O²⁻ → O₂ + 4e⁻
(oxidation is lost electrons)
What do the substances formed at the electrode depend upon in aqueous solutions?
Their reactivity (the less reactive goes to the electrode)
What is formed at each electrode for aqueous potassium bromide (dissolved in water)?
Hydrogen at the negative electrode (cathode) as is less reactive than potassium, bromine at the positive electrode (anode)
What is produced at the cathode if the metal is more reactive than hydrogen?
Hydrogen
What is produced at the anode in an aqueous solution?
Oxygen unless the solution contains halide ions when the halogen is produced
Why does hydrogen get produced when an aqueous solution is electrolysed?
Water molecules break down into hydrogen ions and hydroxide ions
What always happens at the negative (cathode) electrode (HT only)?
Gain of electrons so reduction
What always happens at the positive (anode) electrode (HT only)?
Loss of electrons so oxidation
Write the half equation for the reduction of copper ions.
Cu²⁺ + 2e⁻ → Cu
Write the half equation for the oxidation of chloride ions.
2Cl⁻ → Cl₂ + 2e⁻
Write the half equation for the oxidation of oxide ions.
2O²⁻ → O₂ + 4e⁻
Write the half equation for the reduction of hydrogen ions.
2H⁺ + 2e⁻ → H₂
What technique can be used to measure the volumes of acids and alkalis that react with each other?
Titrations
How do you know when the neutralisation point has been met?
Use an indicator, this will change colour at the neutralisation point.
What piece of equipment is used to measure the variable volume?
Burette
What piece of equipment is used to measure the fixed volume?
Pipette
Examples of indicators.
Phenolphthalein, Methyl Orange, Litmus
How to work out the mass in grams given the volume of solution and concentration in mol/dm³?
- Work out moles using concentration and volume (ensure volume is in dm³).
- Rearrange moles, mass and Mr equation so mass is function and input numbers.
How to work out the concentration from a set of titration results?
- You are very likely to be given a set of results where you need to calculate the mean titre (excluding anomalies).
- Using the concentration and mean titre volume (ensure in dm³), work out the number of moles.
- Use the balanced equation & ratio to work out the number of moles for the concentration you’re trying to work out.
- Using the moles and volume (will be a fixed volume, normally around 25cm³) in the question work out concentration.
