Chemistry Question Thread

Leeshi

Nvm, I figured it out 😅 but just want to check. Is the equation for Sodium thiosulfate reacting with Hydrochloric acid Na2S2O3(aq) + HCl --> NaCl+H2O+SO2+S

Please don't mind the numbers, they're supposed to be subscript ;-;

Thanks, Leeshi.

Billzene

Leeshi you have 2Na on LHS but only 1Na on RHS, so the first equation you gave was correct

Leeshi

Billzene
Thank you for the feedback! 😃

chocomilkenthusiast

Heyoo,

I have my student experiment and my group decided to see what happens to conductivity when the temperature of ethanoic avid solution is increased. I've just got a tiny section of sample calculations to add before I move in my report. Would calculating Ka knowing the concentration H3O+ ions look like this (I'll try and type it out as best I can):
Ka = [H3O+][CH3COO-]/[CH3COOH]
Apparently CH3COO- concentration is equal to H3O+ so I think that explains the next step...
= [H3O+][H3O+]/[CH3COOH]
= [H3O+]²/[CH3COOH]

I have the concentration of CH3COO and also the concentration of H3O+ (via our experimental pH values) so substituting that in should be all good to go?

Billzene

chocomilkenthusiast Good thinking with regards to the formulas, you can also use an ICE table if you’re unsure. I’d like to draw your attention to the fact that Ka is an equilibrium constant, which means it’s dependent on the endo/exo status of the ionisation reaction, so you may need some literature enthalpy values (theoretical accurate values) to assess your accuracy. To complicate things further, the enthalpy value changes depending on the ambient temperature. Just some things to think about here

Billzene

lucy__ FYI the changing enthalpy based on changing temperature thing requires integral calculus (Kirchoff’s Law), so for the sake of your sanity, just look up some values of heat of ionisation for ethanoic acid at different temperatures.

The reason why I had to talk about it is because normally temperature changes don’t incur a sign change in the enthalpy change as in high school you assume heat capacities to be constant regardless of temperature. However, heats of ionisation (enthalpy change for an acid dissociation reaction) are so small that even the smallest temperature change may result in a new deltaH with an opposite sign.

Also, most literature refers to ethanoic acid as “acetic acid”, you’d be surprised how you can’t find anything with the proper IUPAC name but find a million things with its common name.

Leeshi

Hey guyz,

So I need to put a caption under my assignment for safety and ethical considerations but I don't know what to put as my caption. Like I can't put in table 1: safety and ethical considerations. Anyone got ideas for me?

Thanks, Leeshi!

jinx_58

Leeshi
You could just caption it Table 1: Risk Assessment

-jinx_58

Billzene

Leeshi usually with risk assessments you need to give the experiment title as well

Leeshi

Billzene

My title is safety and ethical considerations. However, the teacher wanted a caption below so I have now named it 'Table 1: Risks and management assessment'. I probably didn't do very well 😅

-Leeshi

chemistry1111

how do we balance the positive ions migrating from anode to cathode in electroylsis. since there isnt a salt bridge
if someone could explain

jinx_58

chemistry1111
For galvanic cells, whichever undergoes reduction (i.e. gains electrons) is the cathode, and the one that undergoes oxidation is the anode (i.e. loses electrons).

I suggest you watch these vids, the lad has diagrams, and explains it really really well:
https://www.youtube.com/watch?v=teTkvUtW4SA
https://www.youtube.com/watch?v=7b34XYgADlM
https://www.youtube.com/watch?v=dRtSjJCKkIo

-jinx_58

PhytoPlankton

chemistry1111

I 100% agree with watching those videos @jinx_58 sent. Tyler really does have good visual diagrams. As for the salt bridge, electrolytic cells don't have a salt bridge because it isn't divided into two separate half-cells like galvanic cells. In electrolytic cells, both electrodes are in the same solution which is the electrolyte. The electrolyte facilitates the balance of the charge for electrolytic cells. The videos should explain what I am saying as well.

Hope that makes sense.

chemistry1111

does anyone have any good diagrams to explain galvanic cells because im abit confused on how it works. like how do we know which is anode and cathode based on equations

chemistry1111

thank you also in galvanic cells what does it mean when the switch is closed? would e0 value change if switch open

Billzene

chemistry1111 it means when the circuit is completed. When the switch is open, there’s a break in the circuit such that no current will flow, which means the E cell will be 0, once you complete it, your galvanic cell can now generate electrical energy. E° will still be a theoretical value

Manny

Hi, can someone pls answer this question for me.
Under acidic conditions, tin(II) reacts with hydrogen peroxide to produce tin(IV) and water. Write two half reactions, and hence the net ionic redox equation for this reaction.

Billzene

Manny straight away Sn2+ going to Sn4+ would be an oxidation half reaction given by Sn2+ —> Sn4+ + 2e-

Then H2O2 must be reduced to H2O. Since there’s an oxidation half reaction already, this reaction must be a reduction one. I’ll let you find the half equation with KOHeS and from there combine both half reactions

chemistry1111

does anyone have any hard questions on redox they can upload. thanks

chemistry1111

for the equation 2LIl(aq) + f2(g) —> 2LiF(aq) + I2(g)
i have identified that fluorine gas will be reduced and that I-1 will be oxidised. what would the reductant be? would it be 2LiI(aq) or do you write 2I^-1.

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