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Urgent A/S Chemistry Working out formula

Hi I am stuck on these questions (see attachment)

a) when cooling, the metal oxide rises because its hot so it comes into contact with the hydrogen. otherwise, the metal oxide would jus stay there and not react fully?
not sure.

b) the boat and metal were reheated because the metal could react with the oxygen in air, forming the metal oxide again? so u need to reheat it to convert the oxide bak to the metal by giving the oxide energy to rise as a gas to come into contact with the hydrogen? :/

c)Sn=119?
SnO4

d)SnO4 + 2H2 ---> 4H20 + Sn?

all guesses here... i think im so crap at chemistry. XD