DannyN's chem question thread

[DannyN]

since im always stuck on chem, i figured it'd be more convenient to make a thread and post up questions for help. Thanks in advance for the help guys! my apologies for being such a newb

First one- a multiple choice question
Propane is often used as a fuel in portable barbeques. The equation for the reaction is
C3H8 +5O2 ---> 3CO2 +4H2O
 the reaction is:
a)exothermic and the total chemical energy of the products is less than of the reactants
b)endothermic and the total chemical energy of the products is less than of the reactants
c)exothermic and the total chemical energy of the products is greater than of the reactants
d)endothermic and the total chemical energy of the products is greater than of the reactants

[pi]

a)

Combustion = exothermic = E-products > E-reactants

[b^3]

So since it is a combustion reaction we know that energy is released (since it gets hot). So this means exothermic i.e. a or c
Now for exothermix reactions, the change in H is -ve, so the energy of the products is less than the energy of the reactants (as energy is released). So the answer is A.

EDIT: beaten

[DannyN]

thank you! next one

for the diagram, how does it have be a platinum electrode? are we meant to know this? are there any other kinds of metals we can use?

the question and answer is in the attachment, i can do everything else but im confused about the part regarding the platinum electrode

[b^3]

Yes we are meant to know this. Platinum is mostly for gas electrodes as it catalyses the reaction at that electrode.