CHEMISTRY COMMUNITY

Anna Lockhart 2B

I think for our purposes there is only one type of entropy. There might be more at a higher level of learning.

Anna Lockhart 2B

Does anyone have any suggestions for remembering the different half-life formulas for different order reactions?

Anna Lockhart 2B

A good way to recognize an intermediate is that it is made as a product and then used as a reactant in the next step.

Anna Lockhart 2B

How is a salt bridge represented on a cell diagram?

Anna Lockhart 2B

I like using Goodnotes 5! You can handwrite and then search your handwriting.

Anna Lockhart 2B

Any suggestions for Youtube channels that review chemistry topics (specifically 14B) well?

Anna Lockhart 2B

I agree with what they said, for example if you have an equation A + B -> C and A is first order and B is second order, the overall order would be 3.

Anna Lockhart 2B

From my understanding, you can determine the order of a reaction by plotting concentration data. Depending on the order, the graph will be in a straight line, which alerts you that you have identified the right order.

Anna Lockhart 2B

Does anyone have any good resources for reviewing the rules for balancing reactions?

Anna Lockhart 2B

Does anyone have a quick summary of the difference between galvanic and electrolytic cells?

Anna Lockhart 2B

I remember reduction is gaining electrons by thinking that the charge is "reducing" or becoming more negative.

Anna Lockhart 2B

In lecture, we went over the shorthand for a cell, but it looked like this: w|x || y|z
In this week's sapling, there are two single lines on either side of the double. What do the sections of an expanded shorthand mean?

Anna Lockhart 2B

When dividing Cl2+2Li⟶2LiCl into if half-reactions, Sapling accepts Li⟶Li+e− for the oxidation half-reaction. Why can we ignore the coefficients?

Anna Lockhart 2B

When balancing reactions, I've noticed that we balance acidic solutions differently than basic ones. Why do we do this and what are the differences?

Anna Lockhart 2B

When assigning the oxidation numbers to KClO2, Sapling says we know O2 is 2- and K is 1+ and then we do subtraction to deduct the oxidation number for Cl. Does anyone have a good way of remembering which elements we use subtraction to infer the oxidation number rather than having a set value?

Anna Lockhart 2B

From my understanding, because the temperature is standard (298K), we can replace RT with 0.0592 V and proceed to use the Nernst equation as usual.

Anna Lockhart 2B

I am being asked to balance this chemical equation. I am unsure why Sapling keeps telling me I am wrong.

Anna Lockhart 2B

I have been able to identify the oxidizing and reducing agent for this equation:
[Pb(OH)4]2−(aq)+ClO−(aq)⟶PbO2(s)+Cl−(aq)

Somehow I cannot balance the equation if anyone has any tips!

Anna Lockhart 2B

Could someone walk me through how they balanced this equation:
Cl2O7(g)+H2O2(aq)⟶ClO−2(aq)+O2(g)

I have done it many times and can't seem to get it right.

Anna Lockhart 2B

The question I am given is "What would the potential of a standard hydrogen electrode (S.H.E.) be under the given conditions?"
[H+]=0.49 M PH2=4.5 atm T=298 K

How do I find E° and the Q value for the half-reaction to apply it to the Nernst Equation?

Anna Lockhart 2B

Is it fair to say that larger molecules will always have more disorder than smaller ones?

Anna Lockhart 2B

Under what conditions are we allowed to make deltaS=qrev/T into deltaS=deltaH/T?

Anna Lockhart 2B

In practice problem 4F.9 we are given the pressure changes to find the change in Entropy. How do we apply that to the equation: deltaS=nRln(V2/V1)?

Anna Lockhart 2B

What exactly is Trouton's rule? I saw it on a practice problem and can't remember if we learned it yet.

Anna Lockhart 2B

Wondering how we know which change in entropy equation to use in a reversible reaction versus an irreversible reaction.

Anna Lockhart 2B

When does q=-w?

Anna Lockhart 2B

I saw a post on chemistry community that said if there is no heat transfer q=0. Does this mean there is work done? or does work correlate to volume change?

Anna Lockhart 2B

I am having the same confusion, I ran into this problem in Week 3/4 Sapling #18. I had never seen a Cv or Cp and am confused on what the difference is.

Anna Lockhart 2B

I am having trouble keeping track of the different equations and conditions for q. The ones I have identified are q=deltaH=nCpdeltaT, qsys=-qsurr, qv=deltaU, and deltaU=q+w=0.

Does anyone have a good way of remembering under what conditions these equations are used for?

Anna Lockhart 2B

I thought that deltaU = q+w, but I was unable to solve for the work in this problem. The feedback is saying that deltaU = nCvdeltaT. I guess I have two questions, when are these two equations used? and how do you derive Cv from Cp?

Anna Lockhart 2B

I think it is because it does the maximum amount of work by pushing against the maximum external pressure.

Anna Lockhart 2B

From my understanding, they are not. I know that specific heat capacity is the amount of heat needed to raise the temperature of 1g by 1 degree celcius. I think specific enthalpy is just the energy in the system. It is confusing though that they seem to be used interchangeably.

Anna Lockhart 2B

Are molar and specific heat capacity interchangeable? Are there any instances or equations where you must you one or can they be used in any situation where heat capacity is needed?

Anna Lockhart 2B

If both heat capacity and specific heat capacity measure heat, how is one an extensive property and the other is intensive?

Anna Lockhart 2B

From my understanding the equation you would use is ΔU = Q − W. You then rearrange the equation to solve for Q. (remember that delta U is the change in internal energy and W is the amount of work done by the sysatem)

Anna Lockhart 2B

In Method 2 (bond enthalpies) for finding total enthalpy change, we were told to incorporate the enthalpies of a phase change. How do we know when to include that and what the corresponding value is?

Anna Lockhart 2B

From my understanding, heat is not a state property because the amount of heat used or released depends on the pathway taken. Whereas temperature is only dependent on the initial and final values.

Anna Lockhart 2B

This is because the system has lost energy by performing this work and has therefore lost heat.

Anna Lockhart 2B

I like to think of it as a measure of change. In this case, there is no change because elements are in their most stable state naturally.

Anna Lockhart 2B

Can someone elaborate on the difference between using bond enthalpies and standard enthalpies of formation?

Anna Lockhart 2B

What makes a salt solution different from a regular one? Do we treat them differently when doing equilibrium calculations?

Anna Lockhart 2B

Can someone help define an amphiprotic molecule and how it relates to water?

Anna Lockhart 2B

Depending on if the acid/base is weak/strong we deal with them differently in equations, but how do we determine whether they are strong or weak? Is this something we just have to memorize?

Anna Lockhart 2B

Like they said above, if the x is less than 5% of the initial concentration then you can approximate the x value.

Anna Lockhart 2B

Can someone explain the formula for calculating percent ionization. I remember in lecture we learned that for an acid it is the concentration of the conjugate base over the initial concentration of the acid times 100. For example, [CH3OO-]/[CH3OOH]initial x 100. In a practice problem I was told that...

Anna Lockhart 2B

What does "Stability" imply? In lecture we learned that a large K means the product is more stable and conversely a small K means the reactant is more stable.

Anna Lockhart 2B

Is it ever necessary to know how long it will take for the reaction to create equilibrium in order to solve an equation?

Anna Lockhart 2B

You can think of it as a sort of balance that the reaction is trying to achieve. If there are more moles on the left the reaction wants to get the same amount on both sides, so it will create more products in order to compensate.

Anna Lockhart 2B

So does a change in concentration affect the system in the present? Meaning that it does not affect equilibrium because that constant will remain the same, but it will have an effect on the system before it returns to equilibrium.

Anna Lockhart 2B

I am not sure if this has been taught yet, but how do we determine if a reaction is endo/exothermic?

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