CHEMISTRY COMMUNITY

Daniela Shatzki 2E

hi, I was just wondering when the solutions were going to be posted? thank you! :)

Daniela Shatzki 2E

Yes because if it is dead it is not spontaneous so delta G = 0

Daniela Shatzki 2E

the slowest step of the reaction is the rate-determining step

Daniela Shatzki 2E

I think you can use hours, it just depends on what the question is asking for.

Daniela Shatzki 2E

I'm also not sure if it's going to take place at the same time Sunday for 3 hours like an online quiz or something or a bigger window to turn in?

Daniela Shatzki 2E

Will review sessions and office hours now be canceled?

Daniela Shatzki 2E

if two are given you can't use the formula Ecell = Ecathode - Eanode and then decide which is which based on which arrangement will give you a positive overall value.

Daniela Shatzki 2E

Do we actually have to know how to derive the equation for an exam or just understand what it means/what it does? Should we memorize the final equation?

Daniela Shatzki 2E

You can convert torr to atm by dividing the torr values by 760. The units will then cancel out as you solve the equation. after this do you implement the pressures into the Q equation? I keep getting the wrong overall answer so I'm not sure what I'm doing wrong. Yes, you would plug in the converted...

Daniela Shatzki 2E

is there a specific order that a cell diagram has to be in in terms of phases?

For example:
Cr(s)|Cr3+(aq)||Cl2(g)|Cl-(aq)|C(s)

can the Cl2(g) and Cl-(aq) be switched or does it have to be in this order?

Daniela Shatzki 2E

Ryan Chang 1C wrote:You can convert torr to atm by dividing the torr values by 760. The units will then cancel out as you solve the equation.

after this do you implement the pressures into the Q equation? I keep getting the wrong overall answer so I'm not sure what I'm doing wrong.

Daniela Shatzki 2E

I'm also confused about this, there are many listed for elements such as copper and I'm not sure which to use.

Daniela Shatzki 2E

I think the standard cell potential is the value given by the textbook or other lists while the cell potential is one you calculate.

Daniela Shatzki 2E

kind of reiterating, but when there is no salt bridge the anode loses electrons because it is sending them to the cathode side, therefore the anode becomes more positive and the cathode becomes more negative. therefore, the positive ions from the salt bridge travel to the side with an excess negativ...

Daniela Shatzki 2E

I think you base it off their standard electrode potentials. Use the equation Ecathode - Eanode to determine which way gives you a positive overall Ecell to determine which is the cathode and which is the anode.

Daniela Shatzki 2E

"Test 2 covers 2nd page of Outline 4: Thermodynamics and Outline 5: Electrochemistry and its Applications" this is from the announcements

Daniela Shatzki 2E

this might be a helpful guideline: https://socratic.org/questions/how-do-y ... a-compound

Daniela Shatzki 2E

I agree with what was said above: try to find the elements that generally have the same oxidation states first and assign them their charge so you can then figure out the states of the other elements to make the overall charge zero or satisfy the overall charge of the molecule.

Daniela Shatzki 2E

I think it depends on when you break the equations down, is there a clear one that has something being reduced and a clear one that has something being oxidized. Then you can decide which is the anode and which is the cathode.

Daniela Shatzki 2E

organic chemistry tutor is really good! I always watch his videos for a review, but I wouldn't try to learn everything directly from them as he may not hit everything we need to know.

Daniela Shatzki 2E

kind of reiterating, but the positive ions from the salt bridge travel to the side with an excess negative charge while the negative ions travel to the side with an excess positive charge to balance out the charges to neutral.

Daniela Shatzki 2E

the E cell can be given in a problem, but usually we have to solve it using the standard reduction potentials from the appendix

Daniela Shatzki 2E

Question 7 asks you to find the change in internal energy when the reaction occurs with 1 mole of CO2 being produced. The equation for internal energy is q + w. In order to find q, remember that q equals delta at constant pressure. Using the enthalpy of reaction (-245 kJ per mole of rxn) convert th...

Daniela Shatzki 2E

you raise Kc to whatever you multiply by. if you multiply by 2 then Kc = Kc^2, if you divide by 2 / multiply by 1/2 then Kc = Kc^1/2 or square root of Kc.

Daniela Shatzki 2E

I think generally either both pressure and temperature will be constant resulting only in a change in volume or pressure and volume would be constant resulting in only a change in temperature. If there is a change in volume use nRln(V2/V1), if there is a change in temperature use nCln(T2/T1).

Daniela Shatzki 2E

You need to first write out your balanced equation. The equation that you're going to want to use is w=-PdeltaV. You know that PdeltaV=deltanRT (ideal gas law). From there, you can find that the delta n of the gaseous products is (6-7.5=1.5), and then you just plug in the other values. where did yo...

Daniela Shatzki 2E

I'm confused on question 4J.13: Determine which of the following compounds are stable with respect to decomposition into their elements under standard conditions at 25 °C (see Appendix 2A): (a) PCl 5 (g ) ; (b) HCN (g); (c) NO (g); (d) SO 2 (g) . I don't really understand what it means by stable in ...

Daniela Shatzki 2E

Could someone explain the difference between isothermal, reversible expansion and isothermal, irreversible free expansion? They are mentioned in question 4I.9 on the homework and I'm not really sure what they mean. "Initially an ideal gas at 323 K occupies 1.67 L at 4.95 atm. The gas is allowed...

Daniela Shatzki 2E

I was wondering what the format for midterms are usually like? How many questions are there and is it all free-response or any multiple choice?

Daniela Shatzki 2E

yes, I think it is also the same as the one given on the first test we had.

Daniela Shatzki 2E

I'm kind of still confused about how degeneracy relates to thermodynamics/thermochemistry. Right now, I think understand it vaguely more in terms of quantum mechanics...? Could someone explain the relation between thermo and degeneracy / energy levels / positions / etc.?

Daniela Shatzki 2E

with free expansion, there is no pressure being put on the system and therefore no work can be done because it is not going against any force.

Daniela Shatzki 2E

you don't have to draw out the lewis structures but it is very helpful because then you can visualize which bonds are broken and which bonds are formed.

Daniela Shatzki 2E

I think kJ or J is okay as long as it is consistent

Daniela Shatzki 2E

closed systems can exchange heat/energy with its surroundings but not actual substance. Isolated systems can exchange neither.

Daniela Shatzki 2E

should our homework for this week be from the thermochemistry and first law of thermodynamics section or thermodynamics: second and third laws section?

Daniela Shatzki 2E

If a reaction occurs in a calorimeter and loses heat then that heat cannot go anywhere but stay in the system. Therefore, the calorimeter gains the heat lost by the reaction if that makes sense.

Daniela Shatzki 2E

I think you can use both. If it just says kJ it usually means per mole unless otherwise stated.

Daniela Shatzki 2E

What section should our homework be from for next week? Thermochemistry and First Law of Thermodynamics?

Daniela Shatzki 2E

if the states of the molecules are gas (g) or aqueous (aq) they are involved in the reaction but if the states are liquid (l) or solid (s) they are not included.

Daniela Shatzki 2E

I was kinda confused on how to solve this problem: find the pH of 0.10M (COOH)2(aq) at 25 °C. I solved it one way and got 1.25 as the pH but the answer key says 1.28 so I didn't know if I was close enough or if I did it wrong. I wasn't really sure about how the equation would look for (COOH)2 and H2O.

Daniela Shatzki 2E

if you decrease the volume, that means you are adding more pressure to the system. Therefore, if there are more moles on the left of an equation, decreasing the volume will cause the reaction to go to the right because there are less moles of gas on that side/more space so the reaction will want to ...

Daniela Shatzki 2E

I was wondering if anyone knew the format of tests for this class maybe if you had Lavelle last quarter? Like length-wise and if there's multiple choice or just free response? Also, what is the best way to study?

Daniela Shatzki 2E

the pH scale is 1-14 so the closer to 1, the stronger the acid. therefore, weaker acids will have a higher pH value meaning they are less acidic than strong acids.

Daniela Shatzki 2E

usually when bonds are formed it is more favorable than the atoms being by themselves so therefore they release any extra energy and become more stable.

Daniela Shatzki 2E

next week do we still have homework due in discussion even though there is a test?

Daniela Shatzki 2E

yes, I got that then I did:
85.0 = (0.02+x)(0.03+x)/(0.02-x)(0.04-x)
but then I think I'm just not solving it correctly or something. probably more of a math issue than chemistry haha

Daniela Shatzki 2E

I'm kinda confused about this problem. It gives the initial concentrations for all components and the K and is asking for the equilibrium concentrations so I know you have to find x and then subtract/add it to the original concentrations but I can't seem to find x. I did an ICE table and set the con...

Daniela Shatzki 2E

I believe reactions can reach equilibrium at multiple temperatures but the K changes.

Daniela Shatzki 2E

For the homework due tomorrow can it literally just be any 5 problems? Or should it be like one from each section?

Daniela Shatzki 2E

oh, thank you. I was adding the Ks before.

Daniela Shatzki 2E

I'm not sure if I'm looking at the wrong thing or something but the K I found for the equation in this question from the chart it gives does not match the answer I found in the back of the book. How do you find the K?

Daniela Shatzki 2E

this is unrelated but can someone help me please? I can't figure out how to post something without replying to someone...

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