CHEMISTRY COMMUNITY

Kavvya Gupta 1H

[H2] = 0.066 mol/L
[Cl2] = 1.066 mol/L
[HCl] = 1.868 mol/L
[HCl] = 0.934 mol/L

Kavvya Gupta 1H

Yes, the first elementary step has to be a fast reaction so it can have a bottleneck effect to where you plug in its equilibrium into your rate for the slow so it can match the proposed reaction rate.

Kavvya Gupta 1H

The first equation is written is for any E reaction value at any temperature. The second one is specific to room temperature (25 degrees Celcius).

Kavvya Gupta 1H

for 0 order reaction, k = mol/Ls. For 1st order, k = 1/s. For 2nd order, k = L/(mol s). Overall the units for a reaction should be mol/Ls

Kavvya Gupta 1H

Dhwani Krishnan 1G wrote:do both yield the same results?

Yes if you make sure ln x= 2.303 log x. Otherwise your answers would both be the same

Kavvya Gupta 1H

it's similar to what Lavelle went over on Friday in lecture to where you treat it like a ratio

Kavvya Gupta 1H

it's more common to use log especially when dealing with pH, but otherwise they can be used interchangeably when ln x = 2.303 log x

Kavvya Gupta 1H

Emily Kennedy 4L wrote:how much of electrochemistry do you think it will include?

Whatever we learned today and learn on Friday, I'm assuming.
The test only covers material from week 6 and 7

Kavvya Gupta 1H

There are trends for oxidization states. I expect he will tell us them later but some are:
H is usually +1 unless attached to a less electronegative element then it becomes -1
oxidization of a free element is always 0
oxygen is usually -2 unless in peroxide O2 then its -1

Kavvya Gupta 1H

O2 is naturally occurring so its O. This is the same for H2 and N2

Kavvya Gupta 1H

Aidan Ryan 1B wrote:What are things we have learned that are not state functions?

along with work, heat is also not a state function

Kavvya Gupta 1H

if you mean in terms of K then the reverse reaction would be 1/{K} from the K of the forward reaction. If you mean when solving enthalpy, its H times -1

Kavvya Gupta 1H

the m stands for molar or mass depending on what you are given and what you need to find. If you need to find over kJ/mol and you were given mass you would need to convert to moles. The reason why there is an m is mostly because S is extensive.

Kavvya Gupta 1H

you only ignore the x generally when x<10^-3. Usually, x will be less than 5%, but if it isn't then you would do quadratic as your answer would be slightly off otherwise.

Kavvya Gupta 1H

Gibbs free energy is extensive because it depends on the amount like entropy and enthlapy

Kavvya Gupta 1H

It is correct to take the pKa value and raise it to 10 ^-pKa to get Ka which you can then use for x to solve for [H+] and then take the -log of to get the pH. pKa and pH correlate to the Ka value but are not equal. Ka refers to how much of acid actually dissociates and pKa gives you the acidity of i...

Kavvya Gupta 1H

I know Sonia said she would post the sheet she made with questions that are similar to what questions are going to be on the midterm from today's review session, but I don't know when she's going to post it. Where on Chemistry Community can this worksheet be found? https://lavelle.chem.ucla.edu/for...

Kavvya Gupta 1H

delta u is zero when there is no temperature change

Kavvya Gupta 1H

MMoreno3K wrote:
ariana_apopei1K wrote:Lyndon is probably going to make one that he'll go over in his review session this monday

Do you know where and what time his review session will be?

I believe it's from 7-10 pm at Franz Hall 1178

Kavvya Gupta 1H

I know Sonia said she would post the sheet she made with questions that are similar to what questions are going to be on the midterm from today's review session, but I don't know when she's going to post it.

Kavvya Gupta 1H

This can be seen on the phase change chart during lecture. So boiling water heats up to a high temperature but it is still in liquid phase. The water vapor has to go through a phase change to turn into a gas gaining more energy/temperature into causing it to burn more than boiling water

Kavvya Gupta 1H

you can start thermochemistry if you want too but we are currently still on thermodynamics. I think you will be alright if you turn in homework from thermochemistry though.

Kavvya Gupta 1H

the two equations mean the same thing just written in different ways

Kavvya Gupta 1H

work is a force being applied over a distance. W=fd

Kavvya Gupta 1H

a positive delta u means in an increase in the internal energy due to an increase in temperature
a negative delta u means in a decrease in the internal energy due to a decrease in temperature

Kavvya Gupta 1H

You usually the pressure of a system is at 1 atm when you aren't given any pressure in the question

Kavvya Gupta 1H

Dr. Lavelle will provide us with a sheet with all the constants you need for every test

Kavvya Gupta 1H

if you are given two positive numbers you have to check which x value does not give you a negative concentration when you plug it back in to find the equilibrium concentrations because you can't have an negative concentration

Kavvya Gupta 1H

if the Ka value is below 10^-3 then it is okay to assume that you can get rid of the -x when solving for x because you assume that the change is less than 5%. After solving for x though, just make sure to check that, in fact, it is less than 5% by using the equation x/(acid)initial * 100

Kavvya Gupta 1H

I don't know what the problem says but usually, it will tell you what to solve for in the problem. Given the reaction, you will know what you have to solve for. For instance if it NH3 + H20 -> NH4+ + OH- you would solve for Kb and pOH and if it was HCl + H20 -> Cl- + H30+.

Kavvya Gupta 1H

We don't need to know that equation but for if you do need to convert from Kc to Kp you would use P=MRT and from Kp to Kc M=P/RT

Kavvya Gupta 1H

Kw refers to the concentration while pKw refers to the pH on a scale of 14. pKw comes in handy when you have the pH and you want to find the pOH or vice versa

Kavvya Gupta 1H

you multiply (3.16*10^-3) with (0.114-x) getting 2x= (3.6*10^-4)-(3.16*10^-3)x. Then you get the x on one side getting 2.00316=3.6*10^-4

Kavvya Gupta 1H

The value between 10^-3 and 10^3 does represent a small change either to the left of the right; it's not a very strong change. These values are more important when we get to acids and bases to determine what's a weak or strong acid and base.

Kavvya Gupta 1H

Jordan Lo 2A wrote:Do we need to memorize the formula in the book for converting between the 2?

The only formula you need anyway to convert between the two is the ideal gas law, PV=nRT which changes to P=concentrationRT. It's handy to know, but I don't think you need to memorize it.

CHEMISTRY COMMUNITY

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Re: Test #1

Re: Pre-Equilibrium approach

Re: Nernst Equation

Re: units of rates and rate constants

Re: Nernst Equation (log vs. ln)

Re: 7A. 1 in the 7th edition

Re: Nernst

Re: Test 3

Re: Trends

Re: O2

Re: Delta G a state function?

Re: Reverse Reaction

Re: Delta Srxn

Re: ignoring x validity

Re: Units of Gibbs Free Energy

Re: Acid Base

Re: Study Guides

Re: Delta U

Re: Study Guides

Re: Study Guides

Re: Water vapor vs boiling water burns

Re: HW

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Re: pressure

Re: Acidity & Basicity Constants

Re: correct x from quadratic equation 12.55 6th edition

Re: 5% Rule

Re: pH and pOH

Re: K and Kc (Section 5H.3 7th Edition)

Re: pKw and Kw

Re: Solving for x in ICE table

Re: K values

Re: K and Kc