indicators, acids, bases, alkalis Flashcards
(18 cards)
what is an acid?
a substance which when dissolved in water contains hydrogen ions
the stronger the acid the higher the concentration of hydrogen ions
what ph do acids have?
0-3
acid examples:
hydrohloric acid (hcl), sulfuric acid (h2so4), ethanoic acid (ch3co2h)
what is a base?
a substance that neutralises acid
base examples:
sodium hydroxide (naoh), magnesium oxide (mgo), ammonia (nh3)
what is an alkali?
bases which dissolve in water
what ph do alkali have?
strong: 11-14, weak: 8-11
alkali examples:
sodium hydroxide (naoh), calcium hydroxide (ca(oh)2), ammonia (nh3)
what is the ph scale?
measures the acidity/alkalinity of a substance dissolved in water (0-14)
what phs does everything have?
acidic: <7
neutral: 7
alkaline: >7
what are indicators?
substance that indicate the presence of an acid or soluble base
what colours does litmus paper turn?
acid: red
neutral: purple
basic: blue
what colours does a universal indicator turn?
acid: red
neutral: green
basic: blue
what are salts?
neutral substances formed when an acid and base react.
the hydrogen of an acid has been replaced by a metal
what happens when a metal and acid react?
they form a salt and give off hydrogen
ie metal + acid á salt + hydrogen
eg zinc + sulfuric acid a zinc sulfate + hydrogen
zn+h2so4 á znso4+h2
what happens when acids react with a base/alkali?
they form a salt and water
ie base + acid á salt + water
copper oxide + sulfuric acid á copper sulfate + water
h2so4+cuo á cuso4+h2o
what are carbonates?
when acids react with carbonates, forming a salt and water and giving off carbon dioxide
acid + carbonate á salt + water + carbon dioxide
hydrochloric acid + calcium carbonate á calcium chloride + water + carbon dioxide
2hcl+caco3 á cacl2+h2o+co2
what is neutralisation?
when an acid reacts with a base
slaked lime (calcium hydroxide) neutralises acidity in soil or lakes affected by acid rain
neutralisation reactions are exothermic
