C5: Chemical changes Flashcards
what are ores
rocks from which it is economical to extract the metals they contain
what is the reactivity series
a list of metals in order of their reactivity, most reactive at the top and least reactive at the bottom.
how can we tell if a metal is reactive?
-observing its reaction with water or dilute acid
what happens during a displacement reaction?
a more reactive metal displaces a less reactive metal.
what does an ionic equation show?
the atoms and ions that change in the reaction
what are the two non-metals in the reactivity series?
hydrogen and carbon
oxidation is:
-loss of electrons
OR
-gain of oxygen
reduction is
-gain of electrons
OR
-loss of oxygen
reactions where both oxidation and reduction take place
redox reactions
what are metals often combined with when found naturally
oxygen or sulfur
what are the two ways to extract ores
-reduction of oxide by carbon
-reduction of oxide by hydrogen
explain reduction of oxide by carbon
the metal oxide is heated with carbon and the metal is displaced.
explain reduction of oxide by hydrogen
metals extracted by electrolysis of the molten metal compound
what is a salt
a compound formed when the hydrogen in an acid is wholly, or partially, replaced by metal (or ammonium) ions.
metal + acid ->
salt + hydrogen
what are ions that do not change in the reaction called
spectator ions
the reaction between an acid and a metal is always a _______. why?
redox, metal ions always donate electrons to hydrogen.
general equation for a neutralisation reaction
acid + base -> salt + water
example of an soluble base
alkali
what are bases
compounds that can neutralise acids.
carbonate + acid ->
salt + water + carbon dioxide
acid + alkali ->
salt + water
what do acids release when added to water
hydrogen ions that make the solution acidic
what do alkalis form when added to water
aqueous hydroxide ions, that make the solution alkaline
what’s the difference between a dilute and concentrated acid?
concentrated contains a greater amount of the solute. dilute is same volume but less solute
are carboxylic acids strong or weak
weak
strong acids _______ ionise
completely
weak acids ______ ionise
partially
weak acidic ionising reactions are….
reversible, so some ions recombine to form original molecule
as the concentration of hydrogen ions decreases by a factor of 10….
the pH value decreases by 1 unit
