C4: Chemical Changes Flashcards
What is the order of the reactivity series?
Potassium (K)
Sodium (Na)
Calcium (Ca)
Magnesium (Mg)
Aluminium (Al)
Carbon (C)
Zinc (Zn)
Iron (Fe)
Tin (Sn)
Lead (Pb)
Hydrogen (H)
Copper (Cu)
Silver (Ag)
Gold (Au)
Platinum (Pt)
What is a displacement reaction?
When a more reactive metal displaces a less reactive metal from a compound
What is smelting?
When displacement reactions are used to obtain metals from their ores by displacing with a more reactive, less valuable metal or carbon.
This happens in a blast furnace where the iron oxide is ‘reduced’ to produce iron
What does OIL RIG stand for?
Oxidation
Is
Loss (of electrons)
Reduction
Is
Gain (of electrons
Which pH numbers are acids?
pH<7
Which pH numbers are alkalis?
pH>7
Which pH is neutral?
pH = 7
What happens when an acid and an alkali are reacted completely with each other?
A salt and water are produced
What happens when sulphuric acid reacts with an alkali?
A metal sulphate salt is formed
What happens when nitric acid reacts with an alkali?
A metal nitrate salt is formed
What happens when the salt is left in solution?
We have a mixture of dissociated ions
How do we obtain solid crystals of a dissolved salt?
By heating gently so the water evaporates, leaving only the salt behind
What can we use to measure pH?
Universal indicator
How much is a change in concentration of 1pH?
10x change in concentration of H+ or OH- ions
What makes something acidic?
It’s H+ ions
What makes something alkaline?
It’s OH- ions
What happens to a strong acid in a solution?
It dissociates completely
What happens to weak acids in a solution?
They only partially dissociate
What are 3 examples of weak acids?
-Hydrochloric
-Sulphuric
-Nitric
What are 3 examples of weak acids?
-Ethanoic
-Citric
-Carbonic
What does the pH of an acid depend on?
The strength and concentration of the acid
What are the steps to the titration practical?
-Use a burette to measure what volume of acid/alkali is needed to neutralise
-Measure e.g. 50cm^3 of alkali of known concentration using a glass pipette, put in a conical flask with methyl orange indicator
-Put acid in burette (up to 0cm^3 mark), open tap and let it drip into flask
-Once it goes pink, stop, swirl. If it stays pink, neutralisation has occurred
-(Rough titration can be done before to give more accurate value)
-Use moles to calculate unknown concentration
What does electrolysis involve?
Passing an electrical current through a substance to cause oxidation and reduction at the two electrodes: the anode (+) and cathode (-)
What state do ionic compounds need to be in for electrolysis to take place?
Molten or in a solution so the ions are free to move
