Topic 3 - Chemical Changes
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What do acids form in water?
H+ ions
What does the higher the conc of H+ mean?
The more acidic the solution is
What do alkalis form in water?
OH- ions
What does the higher the conc of OH- mean?
The more alkaline the solution is
What is a base?
A substance which reacts with an acid to produce a salt and water
What is an indicator?
A dye that changes colour depending on whether it’s above or below a certain pH
State the colour of litmus in acid?
Red
State the colour of litmus in neutral?
Purple
State the colour of litmus in alkaline?
Purple
State the colour of methyl orange in acid?
Red
State the colour of methyl orange in neutral?
Yellow
State the colour of methyl orange in alkaline?
Yellow
State the colour of phenolphthalein in acid
Colourless
State the colour of phenolphthalein in neutral?
Colourless
State the colour of phenolphthalein in alkaline?
Pink
What does neutralisation produce?
Salt and water
State the neutralisation ionic equation?
H+ + OH- -> H2O
The pH of an unknown solution is 2 Is the solution acidic or alkaline?
Acidic
How do you investigate the neutralisation reaction of CaO and HCl?
Measure out HCl and CaO Add and then record pH and repeat
What does dissociating H+ mean?
Splitting up to produce hydrogen ions
What are strong acids?
Acids that almost completely ionise in water
What are weak acids?
Acids that partially ionise in solution
What type of reaction is the ionisation of a weak acid?
A reversible one
What are alkalis?
Soluble bases