Acid, bases and salts Flashcards
what is a pH scale
measures acidity and alkalinity
what can a base be
oxides or hydroxides of metals
what can an alkali be
a soluble base
how can pH be measured
pH meter: gives exact pH value
litmus, methyl orange, thymolphthalein- only tell you if acidic not how acidic
universal indicator- gives rough pH
what colour does litmus paper in acid
red
litmus paper in alkali
blue
methyl orange in acid
red
methyl orange in alkali
yellow
methyl orange in neutral
orange
thymolphthalein in acid
colourless
thymolphthalein in alkali
blue
thymolphthalein in neutral
colourless
which acids are strong
HCL
H2SO4
NHO3
which bases are strong
NaOH
KOH
which acids are weak
CH3COOH (ethanoic)
H2CO3
which bases are weak
NH3
metal carbonates
what are oxides
compounds containing oxygen and another element
what are the basic oxides
metal oxides and they react with acids. e.g. MgO
what are the acidic oxides
non-metal oxides and react with bases. e.g CO2, SO2, P4O10
what are the amphoteric oxides
Al2O3 and ZnO they react with both
what are the neutral oxides
CO, N2O they do not react with either
what is definition 1 of acids
acids are compounds that produce hydrogen ions, H+, when dissolved in water.
e.g. when hydrogen chloride gas (HCL) dissolves in water, it dissociates to make hydrogen ions and chloride ions
what is definition 1 of alkalis
alkalis are compounds that produce hydroxide ions when they dissolve in water
what is definition 2 of acids
are proton (H+) donors
what is definition 2 of alkalis
proton (H+) acceptors
how to compare weak and strong acids or alkalis using pH
strong acids have lower pH because there are more hydrogen ions in the solution . The higher the concentration of hydrogen ions, the lower the pH
how to compare weak and strong acids or alkalis using conductivity
strong acids conduct better than weak acids because there are more ions in solution. Similarly, strong alkalis, acids show higher conductivity because there are more ions in solution and have higher pH because there are more hydroxide ions.
which salts are soluble
all sodium, potassium and ammonium salts. All nitrates. Chlorides, bromides, iodides. Sulfates. Sodium, potassium and ammonium carbonates
which salts are insoluble
silver and lead chloride. Calcium, barium and lead sulfate. All other carbonates are insoluble
what is the method of producing salt+ hydrogen
- Add metal to acid
- metal dissolves as it reacts and effervescence is seen
- add metal until no more dissolves
- once effervescence stops and some metal is left. filter off the excess metal.
- evaporate some of the water from the filtrate and let to cool down and crystallise
what is the method of producing salt+ water + carbon dioxide
- add metal carbonate to hot acid
- carbonate dissolves and fizzes as it reacts
- add carbonate until no more dissolves
- once effervescence stops and some carbonate is left, filter off the excess carbonate
- evaporate some water from the filtrate and let to cool down crystallize
what is another method of producing salt+ water
- Add metal oxide to acid
- warm over bunsen burner to dissolve the base
- Add metal oxide until no more dissolves
- filter off excess metal oxide
- evaporate some of the water from the filtrate and let to cool down and crystallise
what is another method of preparing salt + water
titration
1. put the acid in a burette
2. pipette the alkali into a conical flask and add indicator
3. titrate until indicator changes colour and record the volume added
4. repeat the experiment without the indicator using the same volume
5. evaporate some of the water and let to cool down and crystallise
what is a way of preparing an insoluble salt + soluble salt
- Mix two soluble salts and stir
- precipitate forms
- filter the mixture- the insoluble salt is the residue
- rinse the precipitate with water
