Chemical Changes Flashcards
You can measure the pH of a solution, using what?
Universal indicator
Acid + base =
Salt + water
What can acids produce in water?
Produce protons
Acids can be strong or weak
Strong acid (hydrochloric acid) Weak acid (citric acid)
What is pH a measure of?
Measure of the concentration of Hydrogen ions
Factor H+ ion concentration changes by 10^-x
X is the difference in pH. So if pH falls from 7 to 4 the difference is -3, and the factor the H+ ion concentration has increased by is 10^-(-3) = 10^3 = 1000
Do not confuse strong acids with concentrated acids
Acid strength tells you what proportion of the acid molecules ionise in water.
The concentration of an acid is different. It measure how much acid there is in a certain volume of water. Concentration is basically how watered down your acid is.
Acid + Metal =
Salt + water
Acid + metal hydroxide =
Salt + water
Acid + metal carbonate =
Salt + water + carbon dioxide
You can make soluble salts using an insoluble base. Practical.
1) pick right acid and insoluble base, eg to make copper chloride, tou could mix hydrochloric acid and copper oxide
2) Gently warm dilute acid, then turn bunsen burner off.
3) add the insoluble base to the acid a bit at time, until no more reacts. You’ll know when all the acid has been neutralised because, even after stirring, the excess solid will just sink to the bottom.
4) then filter out excess solid to get salt solution
5) to get pure, solid crystals of salt, gently heat the solution using a water bath. Then crystallisation.
Acid + metal =
Salt + Hyrdrogen
Metal + water =
Metal Hydroxide + Hydrogen
Oxidation
Gain of oxygen
2Mg + O2 = 2MgO
Reduction
Loss of oxygen
2CuO + C = 2Cu + CO2
Some metals can be extracted by reduction with carbon. Explain.
Metals below carbon in the reactivity series can be extracted by reduction using carbon.
Metals higher than than carbon in the reactivity can be extracted by reduction using carbon
If electrons are transferred, what is it called?
A redox reaction
This is where reduction and oxidation of electrons happen at the same time
Displacement reactions are?
Redox reactions
A more reactive metal will displace a less reactive metal from its compound
Electrolysis
Splitting up with electricity
What is produced at cathode?
Positive ions and gain electrons (they are reduced)
What is produced at the cathode?
Negative ions and lose electrons (they are oxidised)
Electrolysis of molten ionic solids forms elements
An ionic solid can’t be electrolysed because the ions are in a fixed position and cant move. Molten ionic compounds can be electrolysed because the ions can move freely and conduct electricity.
Metals can be extracted from their ores using electrolysis
If a metal is too reactive to be reduced with carbon or reacts with carbon, then electrolysis can be used to extract it
