Unit 4 questions thread

[charmanderp]

chemderp is right , the strongest oxidant , going up on the left side of the electrochemical series , always reacts with the strongest reductant, going down on the rights ide of the electrochemical series

just circle all the species present in a solution and circle the highest one on the left and the lowest on the right , dont forget h20, and lookout for OH- or H+ if it says acidic/basic environment !

Yeah this is the first thing  do whenever I see an electrolysis question. Write down what species are present.

[joseph95]

whereas with galvanic cells you need to have a 'negative gradient' in order to have a spontaneous reaction ie. the oxidation reaction must be higher than the reduction reaction.

Isn't it the other way around? Yes there's a negative gradient, but the reduction reaction is always above the oxidation reaction in galvanic cells I thought.

[charmanderp]

whereas with galvanic cells you need to have a 'negative gradient' in order to have a spontaneous reaction ie. the oxidation reaction must be higher than the reduction reaction.

Isn't it the other way around? Yes there's a negative gradient, but the reduction reaction is always above the oxidation reaction in galvanic cells I thought.

Right you are!

[joseph95]

[mals22]

Hi, I have a bit of a silly question but it still confuses me till this day.
Eg. Question 4
Dinitrogen tetroxide, N2O4(g), dissociates to form nitrogen dioxide, NO2(g), according to the equation
N2O4(g) 2NO2(g)
0.45 mol of N2O4 gas is placed in an empty 1.00 L vessel at 100°C. When the system reaches equilibrium, there
is 0.36 mol of NO2 gas present in the vessel.
a. Calculate the numerical value of the equilibrium constant for this reaction at 100°C.
How do you figure out how much is remaining.. :/

Thanks for your help in advance.

[thushan]

Hint, for every 2 no2 molecules you form,, you react only one n204. So, since you formed 0.36 mol of no2, how many moles of n2o4 did you react? You know the original amount of n2o4 present. Therefore, how much n2o4 is left?

[soccerboi]

How do you do part c? The answer is apparently 57g but i don't know how to get it.

Thank you for any assistance

[soccerboi]

If the unit of the K value for an eqn is M² and the eqn is reversed and coeffs doubled, then should the units for K of this new eqn be M^-4? I saw in one of the questions in ATARnotes guide, it had M^-2 as the units, so i'm confused about it.

Thanks