help with questions

[dusty_girl1144]

Nope.

cathode:

anode:

Net reaction: zero (usually the case for electroplating)

can i just as a really simple question am i right in summing saying this:

oxidation is the loss of electrons, reduction is the gain of electrons so therefore you know is oxidation when the charge increases and reduction when the charge decreases.

can it also be said : the anode and cathode can also be determined depending on which half equation is high in the electrochemical series? i kinda had a stab at that one... coz i found a constant patten when i was sitting a sac.

[Collin Li]

oxidation is the loss of electrons, reduction is the gain of electrons so therefore you know is oxidation when the charge increases and reduction when the charge decreases.

can it also be said : the anode and cathode can also be determined depending on which half equation is high in the electrochemical series? i kinda had a stab at that one... coz i found a constant patten when i was sitting a sac.

Replace charge with oxidation state (which is closely related with charge).

The second one -- not really, it depends on whether the process is galvanic or electrolytic. Just remember that the anode is oxidation (where electrons are products, because that's when they're "lost") and the cathode is reduction (where electrons are reactants, because that's when they're "gained").

[dusty_girl1144]

ummmm THEM WHAT THE HELL WAS MY TEACHER ON ABOUT!!!???

he said that that could be a way of determining the cathode and anode...


how come it has worked so far for me?

[Mao]

you can determine the cathode or anode, but we first need to know whether it is a galvanic cell or an electrolytic cell.
you are not wrong in saying that the reaction which occurs will be the one higher up (on the left hand side), but there are other considerations such as which species are present, the voltage of the supply for an electrolytic cell, and etc.

[Rosie]

what does 'charge on metal ion in electrolyte' mean?

[Collin Li]

If your electrolyte is for example, the metal ion is the calcium ion, and it has a charge of +2. That is what they mean.

[Rosie]

yep, i thought so.

just want to check if i'm right

electrolyte AgNO₃ silver has a charge of +1
electrolyte Cu(NO₃)₂ copper has a charge of +2
electrolyte Cr(NO₃)₃ chromium has a charge of +3
electrolyte Sn(NO₃)₂ tin has a charge of +2

thank you

[Collin Li]

Correct.

[dusty_girl1144]

galvanic cell i was using it for

[Rosie]

Q. Allowing for experimental error, what is the relationship between the charge on the metal ion present in the electrolyte in a cell and the charge, in coulombs, needed to deposit one mole of metal?

[Mao]

galvanic cell i was using it for

then the strongest oxidant will be reduced, and the strongest reductant will be oxidised, assuming that the cathode (reduction) has a higher E-nought

[dusty_girl1144]

galvanic cell i was using it for

then the strongest oxidant will be reduced, and the strongest reductant will be oxidised, assuming that the cathode (reduction) has a higher E-nought

what i meant was...
could i say:
the anode is the half equation lower in the chemical series and
cathode by the half equation high up in the electrochemical series?

[Rosie]

i think this may be true as the strongest oxident meaning it is a reduction equation is higher up in the series relating to the cathode and vice versa for the anode. But i think you should ask someone else as I'm not sure about this question.

[Rosie]

what does 'the charge of one mole of electrons, in coulomb' mean?

& Q. Allowing for experimental error, what is the relationship between the charge on the metal ion present in the electrolyte in a cell and the charge, in coulombs, needed to deposit one mole of metal?

thanks

[Rawza]

For the first question, do they give you a change in enthalpy? Because if they do, all you probs have to do is find the number of moles through
n = V/Vm (at STP, it is 22.4)
As it asks for  heat of combustion, you only want to find the energy released (assuming its exothermic) by 1 mole. Once you do this and find the number of KJ released for each mole, you can calculate the number of g this equates to. (n= m/Mr) Simplify this, and you get the KJ/g
(while change in enthalpy relates directly to the equation, heat of combustion is only for one mole)

a) A calorimeter should be well insulated in order to ensure that no heat is lost to the surroundings. In calorimetry, we want to find the energy released or absorbed (depending on the experiment), and a loss of heat will cause the energy to be lower than expected.
b) It is necessary to calibrate a calorimeter in order to maintain consistency for the next reaction. While we assume that there are no heat losses, calibration takes the heat losses into account, and provides a more accurate answer