C4 Flashcards
metal carbonate + acid –> ______ +__________ + ______
salt + water + CO2
metal + acid –> _____+____
salt + hydrogen
acid + metal oxide —> ___+ ___
salt + water
what does oxidation mean?
the gain of oxygen
- the substance that gains oxygen has been oxidised
what does reduction mean?
the loss of oxygen
- the substance that lost oxygen has been reduced
PRACTICAL: making pure dry copper sulphate crystals
- measure 25cm^3 of sulfuric acid
- heat gently on bunsen burner, tripod, gauze and heat proof mat
- remove solution from bunsen burner and add copper oxide to acid with spatula and stir
- add excess copper oxide until no more will dissolve
- filter the mixture with filter paper, filter funnel and conical flask
- pour filtered solution into evaporating basin
- leave to dry in cool pace for 24 hours
- remove crystals from solution with a spatula
- gently pat crystals with filter paper
- you now have pure dry crystals of copper sulphate
what is oxidation in terms of electrons?
the loss of electrons
what is reduction in terms of electrons?
the gain of electrons
what is an ore?
a rock that contains a metal compound
what are bases?
chemicals that neutralise acids
what do bases produce?
a salt and water
what do acids produce in aqueous solutions?
hydrogen ions (H+ ion)
what are bases that are soluble in water also called?
alkalis
what do alkalis produce in aqueous solutions?
hydroxide ions (OH-)
which metals are extracted by heating with carbon?
metals less reactive than carbon
which metals are extracted by electrolysis?
metals more reactive than carbon
what 5 are signs a chemical reaction has taken place?
- fizzing
- colour change
- temperature change
- formation of a precipitate
- change in smell
what happens in displacement reaction?
a more reactive element will displace a less reactive element and form a compound
what ion do all salts have?
a positive ion
what is an acid?
a substance that releases H+ ions into solutions
what is an alkali?
a substance that release OH- ions into solutions
practical: why do you heat the acid gently first when making a salt?
to speed up the reaction
practical: why do you stir the solution after adding each spatula of metal oxide?
to make sure it’s fully neutralised
practical: what observation would be made when a metal oxide can no longer react with an acid?
the insoluble metal oxide remained in the beaker
what do strong acids do in solutions?
fully ionise
what are 3 examples of strong acids?
hydrochloric acid, sulfuric acid, nitric acid
what do weak acids do in solutions?
partially ionise in solutuion
what are some examples of weak acids?
methanoic acid and ethanoic acid (vinegar)
concentrated acids have…
have a larger number of acid particles per volume of water
Dilute acids (less concentrated) have…
a smaller number of acid particles per volume of water
what does a lower pH means in terms of hydrogen ion concentration?
lower pH = lower hydrogen ion concentration
what is electrolysis?
splitting up with electricity
what does electrolysis do?
separates elements in insoluble ionic compounds
electrolysis: what are electrodes
solid conductors that are generally made of metal or carbon
electrolysis: where are the electrodes placed and what are they connected to?
- place in a liquid (electrolyte)
- connected to a wire
what is an electrolyte?
a liquid or solution that contains an ionic compound that is molten or dissolved (is free to move)
what are the positive and negative electrodes called?
positive: anode
negative: cathode
what are cations and anions?
cations = positively charged ions (metals)
anions = negatively charged ions (non- metals)
electrolysis: why is the electrode connected to a wire?
so that the electrons can flow between them
electrolysis: why do you need to add a power supply (e.g a battery)
- to drive the flow of electrons
battery is used to pass an electric current through the electrolyte
why do solid ionic compounds not conduct electricity?
because their ions are held in place by strong electrostatic forces of attraction so the ions can’t move
what happens when an ionic compound in melted or dissolved in water?
the forces of attractions are broken and the ions are free to move
electrolysis: what is the negative cathode attached to?
the negative terminal of the power pack
electrolysis: what is the positive anode attached to?
the positive terminal of the powerpack
why is electrolysis expensive?
melting compounds with high melting and boiling points requires a great deal of energy.
- a lot of energy is needed to produce an electric current
what do water molecules form when they are ionised?
hydrogen and hydroxide ions
electrolysis: when is hydrogen produced at the cathode?
if the metal is more reactive than hydrogen
what does aqueous mean?
dissolves in water
electrolysis: what happens if the aqueous solution contains halide ions?
the halogen will be produced at the anode
electrolysis: how can we tell if a gas being produced is a chlorine gas?
if we hold a piece of damp blue litmus paper near the anode and it becomes bleached
why is cyrolite used to dissole (the alluminium oxide)
because it has melting point of over 2000 degrees so it reduces the cost of heating
what must the electrodes be made of?
unreactive/ inert metals/elements
e,g graphite and platinum
why do electrodes have to be replaced every few months?
because it burns away
what is an acid?
a substance that produces H+ ions into solutions
what is an acid?
a substance that produces H+ ions into solutions
what uis
Dont have the steps for electrolysis required practical
