C5: Chemical Changes Flashcards
What happens when different metals react with oxygen?
Group 1/2 metals - vigorous reactions
Transition metals - slow reactions
What is the general equation of metals reacting with oxygen?
metal + oxygen → metal oxide
What is oxidation?
The gaining of oxygen
or the loss of electrons
What is reduction?
The loss of oxygen
or the gain of electrons
What is the general equation for group 1 metals reacting with water?
metal + water → metal hydroxide + hydrogen
Where do hydrogen and carbon go in the reactivity series?
Carbon - between magnesium and zinc
Hydrogen - between iron and copper
How can inert metals be extracted from their ores?
They already come in their pure form because they’re so unreactive
How can relatively reactive metals be extracted from their ores?
Displacement - a more reactive metal will displace the less reactive metal and remove it from its ore form
(carbon is usually used if it’s more reactive because it’s much cheaper)
What is the state symbol usually associated with acids?
aq
What happens to acids in aqueous solutions?
Produce a H+ ion
What are bases usually?
Metal oxides or metal hydroxides (or metal carbonates)
What are alkalis?
Bases which are soluble in water
What happens to alkalis in aqueous solituons?
They produce OH- ions
What does the pH scale show?
The acidity or the alkalinity of a solution
How can we determine the pH of a solution?
pH probe
Universal indicator
Litmus paper
What is the general equation for a neutralisation?
acid + base → salt + water
(H+ from acid and OH- from alkali react to produce water,
more general is H+ + OH- → H2O)
What is the general equation for acids reacting with metals?
acid + metal → salt + hydrogen
How does the reactivity of a metal affect how quickly it reacts with an acid?
The more reactive it is, the faster it reacts as it displaces hydrogen more quickly
Give an example of an oxidation and reduction equation in relation to acids reacting with metals
2HCl + Mg → MgCl2 + H2
Oxidation = Mg → Mg2+ + 2e
Reduction = 2H+ + 2e → H2
What are the products when acids react with metal carbonates?
salt + water + carbon dioxide
What is the difference between strong and weak acids?
Weak acids partially dissociate when dissolved in water, strong acids fully dissociate in water
What are examples for the equations for the ionisation for weak and strong acids?
Strong = HCl →H+ + Cl -
Weak = H2CO2 → H+ + HCO3-
←
What are 3 examples of weak acids?
Carbonic acid
Ethanoic acid
Citric acid
What does the pH scale tell about the concentration of H+ ions in acids?
Strong acids have a lower pH for a given concentration, as they produce a greater conc. of hydrogen ions
What is the pattern followed by the pH scale?
As the pH scale decreases by 1 unit, the concentration of hydrogen ions increases by 10 times
e.g. pH 1 has a 10x greater conc. of H+ than pH 2
Describe the process of carrying out a titration
Use a pipette to transfer 25cm³ of the alkali into a conical flask (reduces risk of splashing). Add 5 drops of indicator to the conical flask and place the flask on a white tile. Fill a burette with sulfuric acid, and place the conical flask under the burette. Slowly release the acid from the burette until a colour change is seen (swirl the conical flask while doing so)
How do you calculate a titre?
New amount - staring amount
