Chemistry C4
Acids and Bases:
The Ph scale:
Goes from 0 to 14, with 0 being highly acidic and 14 being highly alkaline. A universal indicator can be used to measure the Ph of a solution.
Neutralising
Acids and Bases neutralise one another, A base is any substance that will react with an acid to form a salt.
Acids + Base = Salt + Water
Water has a ph of 7 - This is called the neutral Ph
All products from a neutralisation reaction are neutral
Titration - Required Practical
Titrations are used to find the concentration of a solution. They allow you to determine what amount of acid is required to neutralize a volume of alkali.
Method
Use the pipette and pipette filler to add 25 cm3 of alkali to a clean conical flask.
Add a few drops of indicator and put the conical flask on a white tile (so you can see the colour of the indicator more easily).
Fill the burette with acid and note the starting volume.
Slowly add the acid from the burette to the alkali in the conical flask, swirling to mix.
Stop adding the acid when the end-point is reached (the appropriate colour change in the indicator happens). Note the final volume reading.
Repeat steps 1 to 5 until you get consistent readings
The same method works for adding an alkali to an acid - just swap around the liquids that go into the conical flask and burette.
Titrations should be related to increasing the accuracy. The first titration should be a rough titration, with the ones after being more accurate to within 0.10 cm^3.
A single indicator should be sued to determine a sudden colour change. such as Phenolphthalein, litmus or methyl orange
Strong acids, Weak Acids and their reactions:
Acids can be strong or weak. Strong acids ionise completely in water. All the acid particles dissociate to release h+ ions.
Strong acid: Hcl = H+ + cl-
Weak acid: ch3cooh = (revisable rection to) = h+ ch3coo-
The Ph is a measure of the concentration of H+ ions in the solution.
For every Ph decrease of 1, the concentration of H+ ions increase by a factor of 10
Strong acids are not concentrated acids! Concentration is a measure of how much acid there is in a volume of water. Acids can be dilute or concentrated. Ph will decrease with an increase in concentration regardless of how strong or weak the acid is
Metal oxides and Hydroxides:
Are bases. Some dissolve in water, these soluble commands are alkalis, as alkalis react with acids in neutralising reactions.
Acids and Metal carbonates produce carbon dioxide
Metal carbonates are also bases, they will react with acids to produce a salt, water and carbon dioxide.
Metals and their reactivity:
The reactivity series:
List of metals in order of how receive they are. Their reactivity is determined by ho easily they loose electrons.
Reactivity series: 
How metals react with acids tells you about their reactivity.
Some metals react to produce hydrogen and salt.
The speed of the reaction is determined by the rate at which the hydrogen gas is given off, This speed indicates how reactive a metal is.
Metals also react with water: Metals react to give a metal hydroxide and hydrogen gas. Only the more reactive metals react with water.
Metals often have to separated from their oxides:
Most metals are not found pure, they are found in ore form and have to be extracted and refined.
Formation of metal ore: Oxidation is a gain of oxygen
Extraction of metal: Reduction is a loss of oxygen
Some metals can be extracted by reduction with carbon:
Magnesium and above can be entreated by electrolysis, Anything below carbon can be displaced by carbon and reduced by reaction with carbon.
Redox reactions:
A loss of electrons is called oxidation
A gain of electrons is called reduction
Aogram - OIL RIG
REDuction and Oxidation happen at the same time, Hence the name REDOX reactions
A MORE reactive metal will displace a LESS reactive metal from its compound
Ionic equations can be used to show redox reactions.
E.g Mg + ZnCl = Mgcl + Zn
Only used to show the useful sections of a reaction
Electrolysis:
Means splitting up with electricity
An electronic current is tased through an electrolyte. The electrolyte is a molten or dissolved ionic compound. The positive ions move towards the elctrons, where they react, and the compound decomposes. The positive ions move to the cathode and gain electrons. The negative ions move towards to anode where they lose electrons. This creates a flow of charge as the ions travel through the electrolyte.
An ionic solid can't be electrolysed, it must be dissolved or molten. This means the ions can move freely and conduct electricity.
Electrodes should be made of an inert material to avoid them reacting with the electrolyte.
Metal electrolysis:
Metals can extract from their ores using electrolysis. If a metal is to reduce carbon or reacts with carbon, Electrolysis can be used. It is very expensive as lots of energy is required to melt ores.
At the positive electrode: If the negative ion from the ionic compound is simple (eg Cl- or Br-), then that element is produced. If the negative ion is a complex ion (eg NO3-, SO42-, CO32-), then oxygen is produced from the hydroxide ion present instead.
At the negative electrode: Metal ions and hydrogen ions are positively charged. Whether you get the metal or hydrogen during electrolysis depends on the position of the metal in the reactivity series.
Ionic half equations can be used as notation for the reactions occurring at either the cathode or anode during electrolysis
E.g Al3+ + 3e- = Al
Electrolysis of an Aqueous solution:
When electrolysing in water, the ions in the water have to be factored in.
As well as the ions from the ionic compound there are hydrogen ions and hydroxide ions from the water.Te ions discharged at each electrode depends on the reactivity of the ions.
Cathode Rule : If H+ ions are present ten hydrogen gas is produced, if the elemental metal formed is less reactive then a layer of the metal ion will form around the cathode.
Anode rule: If an OH- and halide ion are present (cl-, br-,i-), molecules of chlorine, bromine, and iodine will be formed
If no halide ions are present then Oh- ions will be discharged from the water as oxygen and water.