Topic 8 - Acids Flashcards
Describe red litmus paper colour changes
Acid: red
Neutral: red
Alkali: blue
Describe blue litmus paper colour changes
Acid: red
Neutral: blue
Alkali: blue
Describe methyl orange colour changes
Acid: red
Neutral: yellow-orange
Alkali: yellow-orange
Describe phenolphthalein colour changes
Acid: colourless
Neutral: colourless
Alkali: pink
What is universal indicator used for
To approximate pH
It is a broad range indicator
Goes from red -> green -> blue
A combination of dyes
What is an acid?
H+ donor (proton donor)
What is an alkali
OH- donor
A soluble base
What is a base
H+ acceptor (proton acceptor)
Metal oxide/hydroxide
Alkalis that are insoluble in water
Describe the general formula for (dilute) acid + metal reactions
Acid + metal -> salt + H2
What is a salt?
A compound formed when a hydrogen is displaced from an acid
An ionic compound formed during a neutralisation reaction
Which metals are not reactive enough to react with an acid
Copper, silver and gold
Which metals are too reactive to react with an acid
Potassium, sodium, lithium and calcium
Describe the general formula for acid + base reactions
acid + base -> salt + water
Describe the general formula for an acid + carbonate reaction
Acid + carbonate -> salt + water + carbon dioxide
What is limewater?
Saturated calcium hydroxide solution
How to prove the metal reactivity trend?
1) set up 3 boiling tubes and fill them with equal volumes of dilute HCl/H2SO4
2) place pieces of magnesium, zinc and iron into separate test tube (control size, shape, mass)
3) the speed of reaction is indicated by rate at which bubbles of hydrogen are given off
4) confirm the hydrogen with the squeaky pop test
Describe the pH scale
0-3: strongly acidic 4-6: weakly acidic 7: neural 8-10: weakly alkaline 10-14: strongly alkaline
What is an indicator?
A dye which changes colour
What colour is plain litmus in neutral solutions?
Purple
Describe the equation for acid + base neutralisation
H+ (aq) -> OH- (aq) -> H2O (l)
The acid donates the protons which are accepted by the base. The products are always neutral.
Describe the equation for acid + ammonia
Acid + ammonia -> ammonium salt
E.g: HNO3(aq) + NH3(aq) -> NH4NO3(aq)
