Atomic Structure and the Periodic Table Year 10 Flashcards
describe the trend in reactivity in group 1 elements as you go down the group
increasing reactivity, lower melting and boiling points, higher relative atomic mass
state the word equation for the reaction of water and a group 1 metal (sodium)
sodium + water -> sodium hydroxide + hydrogen
state the word equation for the reaction of chlorine and a group 1 metal (sodium)
sodium + chlorine => sodium chloride
state the ionic equation for the reaction for the electrolysis of lead bromide at the anode and the cathode
anode :
Pb2+ + 2e- –> Pb
cathode:
2Br- –> Br2 + 2e-
why can ionic solids only be extracted in molten state?
- when solid, ions are in a fixed position and cant move.
- in a liquid state the ions can move around freely to conduct electricity (needed for electrolysis)
name the ore aluminium is found naturally in and what compound is contained in it
bauxite
al2o3
give a disadvantage of extracting metals from their ore
it is very expensive as lots of energy is needed to melt the ore
why is cryolite added to bauxite when extracting aluminium
- contains Al2O3 which has a v. high melting point.
- lowers the melting point, reducing the amount of energy needed to melt bauxite, reducing the cost of the process
describe the electrolysis of aluminium from its ore
- the molten mixture contains free ions so conducts electricity
- cathode attracts positive al+3 ions
- they gain 3 electrons (reduced) and form neutral al atoms which sink to the bottom of the tank
- anode attracts negative o2- ions
- they lose 2 electrons (oxidised) making neutral oxygen atoms forming o2 molecules
state the ionic equation for aluminium extraction at the cathode
Al3+ + 3e- –> Al
state the ionic equation for aluminium extraction at the anode
2O2- –> O2 + 4e-
state the ionic equation for aluminium extraction
2AL2O3 –> 3O2 + 4AL
define reduction in terms of electrons and oxygen
reduction is a gain of electrons and a loss of oxygen
define oxidation in terms of electrons and oxygen
oxidation is a loss of electrons and a gain of oxygen
define a redox reaction
a reaction where reduction and oxidation happens at the same time
give an example of a redox reaction (general word equation)
acid + metal –> salt + hydrogen
recall the reactivity series
potassium sodium lithium calcium magnesium aluminium zinc iron copper silver gold
how do you measure reactivity (method)
- measure temp change of the reaction between the acid/water and metal over a set period of time.
- the more reactive the metal, the higher the temp change
state the general word equation for the reaction between metal and water
metal + water –> metal hydroxide + hydrogen
state the general word equation for the reaction between group 1 metals and water (where X represents the metal)
2X + 2H2O –> 2XOH + H2
state the general word equation for the reaction between group 2 metals and water (where X represents the metal)
X + 2H2O –> X(OH)2 + H2
why is the relative atomic mass of chlorine a decimal?
- chlorine exists as different isotopes (different numbers of neutrons) so the ar is an average.
- takes into account the diff. masses and amounts of the isotopes that make up the element
what is the avragado constant?
6.02 x 10 to the power of 23 particles
state the formula to work out moles
moles = mass / mr
