Topic 4: Chemical changes Flashcards
what happens in a displacement reaction?
a more reactive metal displaces a less reactive metal from a compound
which non-metals are also included in the reactivity series?
hydrogen and carbon
what determines how reactive a metal is?
how easily they lose electrons- forming positive ions, the higher up the reactivity series a metal is the more easily they lose electrons
what is the order of the reactivity series?
potassium, sodium, lithium, calcium, magnesium, carbon, zinc, iron, hydrogen, copper
zinc + hydrochloric acid –>
zinc chloride + hydrogen
because the zinc is more reactive than the hydrogen
what happens when magnesium reacts with dilute acid?
lots of bubbles are given off telling us that magnesium reacts vigorously
what is oxidation?
gain of oxygen
eg 2Mg + O2 –> 2MgO
what is reduction?
loss of oxygen
eg 2CuO + C –> 2Cu + CO2
copper + hydrochloric acid –>
copper + hydrochloric acid
as the copper is less reactive than thew hydrogen
what are metals found as?
unreactive metals like gold are found in the Earth as the metal itself but most metals are found as compounds that require chemical reactions to extract the metal
how can you extract metals less reactive than carbon?
by reduction with carbon
what is the process of electrolysis?
when an ionic compound is melted or dissolved in water the ions are free to move about within the liquid or solution. These solutions are able to conduct electricity and are called electrolytes.
passing current through electrolytes causes the ions to move the electrolytes. positively charged ions move to the negative electrode (the cathode) and negative ions move to the positive electrode (the anode). Ions are discharged at the electrodes producing elements.
if lead bromide is electrolysis what will be produced at the + and - electrode?
\+ = bromine - = lead
when can electrolysis be used and why does it use large amounts of energy?
1) metals can be extracted from molten compounds using electrolysis. electrolysis is used if the metal is too reactive to be extracted by reduction with carbon or if the metal reacts with carbon
2) large amounts of energy are used in the extraction process to melt the compounds and product electrical currents
how do you prepare aluminum for electrolysis?
you make a molten mixture of aluminum oxide and crytolite using carbon as the positive electrode (anode)
why should a mixture be used and why does the anode have to be constantly replaced?
a mixture is used because this allows the ions something to move in
the electrode must be replaced because the oxygen from aluminum oxide reacts with the carbon it is made out of producing aluminum oxide therefore wearing away the carbon
what happens at the cathode and anode?
at the cathode positively charged ions gain electrons and so the reactions are reduction
at the anode negatively charged ions lose electrons and so the reactions are oxidations
what is half equation for reduction with hydrogen?
2H2+ +2e- –> H2
what is the half equation for oxidation with hydroxide?
4OH- + 4e- –> O2 + 2H20
what is oxidation and reduction?
oxidation = loss of electrons reduction = gain of electrons
roses are red,
GCSE’s give me pain,
Oxidation is loss,
Whilst reduction is gain, (going to get a 9 in English)
what happens at the anode and cathode when an aqueous solution is electrolysis?
cathode:
hydrogen is produced if the metal is more reactive
anode:
oxygen i produced unless the solution contains halide ions (group 7 ions)
This happens because in the aqueous solution water molecules break down producing hydrogen ions and hydroxide ions that are discharged
what do some acid react with metal to make?
salt and hydrogen
what forms when a acid reacts with an alkali?
water and salt
what forms when a acid reacts with and metal carbonates?
salt, water and carbon dioxide
what is the PH scale measured in, what does it measure and what is it measured with?
- 0 to 14
- how acidic/ alkali a solution is
- universal indicator
what PH is an acid, alkali and neutral solution?
acid: less than 7
alkali: more than 7
neutral: 7