A couple chem questions ~

[crayolé]

How does one go about solving these types of questions? (attached)

Also, why is this equation for the aqueous solutions always neglected? It's always the other two water equations being used
O2 + 2H2O + 4e-----> 4OH

[Martoman]

FIRST -> That equation is neglected because OXYGEN is reducing, not water. That is sneaky as, good question.

Secondly, lovely logic tells us that its either A or D as K+ is below the water equation, meaning water will preferentially reduce in the third beaker. Thus no K is reduced at the cathode.

Since its the same electrcity throughout all, the same amount of mol of electrons are being passed through.

Silver has one electron per ion and copper 2 as per the equations in the elctrocehmical series.

Mole ratio is, from left to right,

0.5:1:0

(multiply it by 2)

1:2:0

So it can't be A, A is a trap for students who do'nt read the question and think they are done once they get that line out, hence D. If you want thourough working then simply convert the ratio of mols to a ratio of mass

63.6 : 107.9*2: 0

Divide by smallest

1: 107.9*2/63.6:0

1:3.4:0

Again, D.