C5 Chemical Changes Flashcards
What is an ore?
A rock which contains enough metal to make it economically worthwhile to extract
What is the reactivity series?
A list of metals in order of their reactivity, with the most reactive at the top and the least reactive ones at the bottom
How are metals put in order of reactivity?
Looking at their reactions with:
Water
Dilute acid
What gas is given off when metals react with water or dilute acid? What is the test for it?
Hydrogen
It pops with a lighted splint
what is formed when metals react with oxygen?
metal oxides
what is gaining oxygen called?
oxidation
what is losing oxygen called?
reduction
what does reacting a metal with water produce?
metal hydroxide and hydrogen
what affects how reactive a metal is?
it depends on the metal’s ability to lose electrons and form a positive ion
how are unreactive metals found?
by themselves as they are so unreactive
what does displacement mean?
a more reactive element will push out (displace) a less reactive element from its compound
why is carbon used in extracting metals?
it is very cheap
what is OILRIG?
oxidation is loss (of electrons)
reduction is gain (of electrons)
what does (aq) mean?
aqueous solution - dissolved in water
what do acids produce in aqueous solutions?
hydrogen ions (H+)
what is a base?
a chemical which can neutralise and acid producing a salt and water
what are bases usually?
metal oxides or metal hydroxides
what is an alkali?
a base which is soluble in water
what ions do alkalis form in aqueous solutions?
hydroxide ions (OH-)
what is the range of pHs for acids?
0 - <7
what is neutral on the pH scale?
7
what is the range of pH values for alkalis?
> 7 - 14
what happens to the H+ and OH- ions in a neutralisation reaction?
they react to produce water
what do all acids contain?
hydrogen
what can metals before hydrogen on the reactivity series do?
displace hydrogen
what is the general equation for an acid reacting with a metal?
metal + acid –> salt + hydrogen
what salts does hydrochloric acid produce?
ones ending in -chloride
what salts does sulfuric acid produce?
ones ending in -sulfate
how does magnesium react with acids?
rapidly as it is high up on the reactivity series
magnesium also easily forms ions so the reaction is rapid
how does zinc react with acids?
quite rapidly as it is more reactive than hydrogen
zinc also forms ions quite easily so reacts quite rapidly
how does iron react with acids?
fairly slowly as it is only more reactive than hydrogen by a small amount
iron does not easily form ions so the reaction is slow
which molecules are reduced and which are oxidised when a metal reacts with an acid?
hydrogen ions are reduced (they gain electrons) and become hydrogen gas
metal atoms are oxidised (lose electrons) to become metal ions
what is produced when a base or alkali reacts with and acid?
salt and water
what does nitric acid produce?
salts ending with -nitrate
what ions do salts contain?
a positive ion from the base or alkali
a negative ion from the acid
what are the products of a metal carbonate reacting with an acid?
salt
water
carbon dioxide
what does ionised mean?
when a molecule splits into ions in water
e.g. when an acid molecule splits into hydrogen ions and negative ions
what is a strong acid?
an acid where the acid molecules fully ionise in aqueous solutions
what is a weak acid?
an acid where the molecules partially ionise in aqueous solutions.
the reaction is reverseable
what does the pH scale say about hydrogen ions?
it gives an idea of the concentration of hydrogen ions
how do pHs differ with strong and weak acids?
strong acids have a lower pH than weak acids for a given concentration.
this is because a strong acid has more hydrogen ions as they fully ionise
what happens when the pH scale decreases by 1 unit?
the concentration of hydrogen ions increases by 10 times
what does the concentration of an acid tell you?
the amount of acid molecules in a given volume of solution
