CC8 - Acids And Alkalis Flashcards
what is the PH scale
a measure of how acidic or alkaline a substance is
what is the PH of a neutral substance
7
what are acids
- a substance with a PH less than 7
- forms H+ ions in water
explain the strength of an acid in terms of H+ ions
- stronger acids have a higher concentration of H+ ions
- as the concentration of H+ ions increases, the PH of the acid decreases
what is a base
a substance that reacts with an acid to produce salt and water only
what is an alkali
- a base that is soluble in water
- have PH greater than 7
- form OH- ions in water (hydroxide ions)
explain the strength of an alkali in terms of OH- ions
- stronger alkalis have a greater concentration of OH- ions
- as the concentration of OH- ions increases, the PH of the alkali increases
what is an idicator
a dye that changes colour depending on whether the PH of a substance is above or below a certain PH
colours of universal indicator in: acids, neutral, alkalis
acid: strong = red, weak = yellow
neutral: green
alkali: strong = purple, weak = blue
colours of litmus indicator in: acids, neutral, alkalis
acid: red
neutral: purple
alkali: blue
colours of methyl orange indicator in: acids, neutral, alkalis
acid: red
neutral: yellow
alkali: yellow
colours of phenolphthalein indicator in: acids, neutral, alkalis
acid: colourless
neutral: colourless
alkali: pink
what is the reaction between an acid and a base called
neutralisation
neutralisation rection formula
acid + base —–> salt + water
ionic equation of neutralisation reactions in aqueous solutions
H+ + OH- —–> H20
what is the PH of the products of a neutralisation reaction, why
PH 7
- the concentration of H+ and OH- ions is equal