Chemical Changes Flashcards
what are alkalis?
soluble bases
which pH is most acidic?
0 or 1
which pH is most alkali?
13 or 14
which pH is neutral?
7
which ions do acids produce?
H+ ions in water
which ions do alkalis produce?
OH- ions in water
what are 2 ways to measure pH?
1: universal indicator - a wide range indicator that changes colour depending on the pH. It gives an approximate pH value
2: pH probe - gives an accurate value of the pH
what is the neutralisation reaction?
acid + base > salt + water
H+ + OH- > H2O
what are titrations?
used to find the exact volume of acid needed to neutralise a quantity of alkali (or vice versa). the results can be used to calculate the acid or alkali concentration.
what is the metal carbonate reaction?
acid + metal carbonate > salt + water + carbon dioxide
what is the metal oxide reaction?
acid + metal oxide > salt + water
what is the metal hydroxide reaction?
acide + metal hydroxide > salt + water
how are soluble salts made?
by adding metals or insoluble metal compounds to acids. The excess solid is filtered off and the remaining salt solution is crystallised.
what is a strong acid?
an acid that completely ionises (dissociates) in water to produce hydrogen ions
- hydrochloric acid
- sulfuric acid
- nitric acid
what is a weak acid?
an aci that partially ionises (dissociates) in water to produce hydrogen ions
- ethanoic acid
- citric acid
- carbonic acid
what is pH?
a measure of the concentration of H+ ions in a solution
what happens when the pH of a solution changes by X?
the H+ ion concentration chages by a factor of 10^-x
what is acid strength?
a measure of the proportion of acid molecules that ionise in water
what is acid concentration?
a measure of the number of acid molecules in a certain volume of water
which metals of the reactivity series can be exracted from molten compounds using electrolysis (top 5)?
Potassium
Sodium
Lithium
Calcium
Magnesium
what comes after the electrolysis 5?
carbon
which 3 can be extracted from their oxides by reduction using carbon?
Zinc
Iron
(Hydrogen)
Copper
what is the metal + oxygen reaction?
metal + oxygen > metal oxide
what is the metal + acid reaction?
metal + acid > salt + hydrogen
what is the metal + water reaction?
metal + water > metal hydroxide + hydrogen
which elements have an explosive reaction to cold, dilute acid AND a reaction to water?
Potassium
Sodium
Lithium
Calcium
which elements have a moderate reaction to cold, dilute acid BUT no reaction to water?
Magnesium
Zinc
Iron
which element has no reaction to either cold, dilute acid OR water?
copper
what is a displacement reaction?
when a more reactive element displaces a less reactive metal from its compound
what is oxidation?
gain of oxygen
loss of electrons
what is reduction?
gain of electrons
loss of oxygen
what is a redox reaction?
where one substance in a reaction is reduced and another is oxidised
Fe + CuSO4 > FeSO4 + Cu; which is the oxidation and which is the reduction?
Fe loses 2 electrons to become Fe2+ + 2e- so it’s oxidised
Cu2+ gains 2 electrons to become Cu so it’s reduced
what are ionic equations?
they only show the particles that react and the products they form
what is the ionic equation of magnesium + aqueous zinc chloride > aqueous magnesium chloride + zinc?
Mg + Zn2+ > Mg2+ + Zn
what would we call the chloride ions?
spectator ions
what is an electrolyte?
a liquid or solution that can conduct electricity because ions are free to move
what happens to the positive metal ions (Pb2+)?
they move towards the cathode and are reduced
Pb2+ + 2e- > Pb
what happens to the negative non-metal ions (Br-)?
they move towards the anode and are oxidised
2Br- > Br2 + 2e-
what happenes in the electrolysis of aqueous CuSO4?
metal produced at the cahtode if it is less reactive than H2
O2 and H2O are produced at anode if no halide ions are present
what happens in the electrolysis of aqueous NaCl?
H2 produced at the cathode if metal is more reactive than H2
Halogen produced at the anode if halide ions are present
