CHEMISTRY COMMUNITY

MichaelMendozaD1F

A constant‑volume calorimeter was calibrated by carrying out a reaction known to release 2.22 kJ of heat in 0.300 L of solution in the calorimeter (q=−2.22 kJ) , resulting in a temperature rise of 3.52 ∘C . In a subsequent experiment, 150.0 mL of 0.30 M HClO2(aq) and 150.0 mL of 0.30 M NaOH(aq) were...

MichaelMendozaD1F

For atoms that are more polarizable, the bigger the atom is = the more polarizable. I like to remember this by thinking of an analogy where I'm trying to pop balloons with a dart. The bigger the balloon, the more likely I'll be when I throw a dart to pop it (influence its e- cloud). For polarizing ...

MichaelMendozaD1F

Hello! Why is -log(x) the same as the original pH? I thought it would be the difference between pH1 and pH2. Thank you! Hi! So, the whole thing about pH is that it's the -log of the concentration of H + . Like Lavelle said in lecture, the "p" means that you take the -log. For example, pK ...

MichaelMendozaD1F

Brendan Duong 1I wrote:
MichaelMendozaD1F wrote:are ALL bent molecules polar?

Yes I believe all bent molecules are polar. The shape makes it so that dipoles can never cancel

thank you ! I appreciate the response!

MichaelMendozaD1F

Moura Girgis 1D wrote:
MichaelMendozaD1F wrote:is most "stable" the same as most likely or favorable? I believe they are synonymous in these types of problems but I just want to make sure.

yes, more stable lewis structures also tend to be those with the lower formal charge, so they are more favorable .

thank you for the response !

MichaelMendozaD1F

so would amine have two m's?

MichaelMendozaD1F

is most "stable" the same as most likely or favorable? I believe they are synonymous in these types of problems but I just want to make sure.

MichaelMendozaD1F

Here is a helpful little way to remember, but I believe it is also realllyyyy important to understand why the hybridization occurs rather then memorize the numbers. https://d3i71xaburhd42.cloudfront.net/ac73a46dc482862c4baa12b73f648f3dd3fa5989/28-Table1-1.png The attachments ^ means the number of b...

MichaelMendozaD1F

how do you check to see if your bond angles are correct? or how to find them in general?

MichaelMendozaD1F

are ALL bent molecules polar?

MichaelMendozaD1F

Can someone explain the concept of resonance as well as how to find resonance structures? resonance and resonance structures are alternative modelings of compounds which may have different charges. Structures can also be labelled as having lower energy (more favorable) and higher energy (less favor...

MichaelMendozaD1F

Hi! Does anyone have a good way to remember what makes an atom/ion more polarizable and which atoms/ions have more polarizing power? I'm having a little trouble with those concepts. For atoms that are more polarizable, the bigger the atom is = the more polarizable. I like to remember this by thinki...

MichaelMendozaD1F

Kat Stahl 1L wrote:I thought it was just the smaller the difference in electronegativity the more covalent character that bond has.

I also thought this to be true but I suppose there are multiple ways of determining covalent character ?

MichaelMendozaD1F

What exactly is the significance of a delocalized bond? are there differences in strength between delocalized and localized ?

MichaelMendozaD1F

will we be expected to determine hybridization from lewis structures and compounds, (ClSO4) for example, on an exam?

MichaelMendozaD1F

will spin state ever be on a final exam? I mean will we have to give the spin state by hand to the sub shell level?

MichaelMendozaD1F

So do we always take the placement on the periodic table first, or simply look to electronegativity, if given?

MichaelMendozaD1F

Will we be expected to know or compose a lewis structures when given the name of the compound, such as "periodate ion" etc., on Midterm 2?

MichaelMendozaD1F

Along with what everyone else has already said, a rough guideline for finding out if a bond is ionic or covalent is to find the difference in electronegativity between the two molecules. If the difference is greater than 2 then the bond is ionic, whereas if the difference is less than 1.5, the bond...

MichaelMendozaD1F

How do you classify if a compound is a Lewis acid or base when given the chemical formula? Hi Michael! I had the same issue that you had in classifying the compounds, especially in Sapling. However, a quick note that might make it easier for you is that lewis acids are atoms that accept or take ele...

MichaelMendozaD1F

how do we arrange bonds according to length? I believe this was in the sampling hw Q11. Bond length depends on the type of bond (single, double, triple) and the sizes of the atoms involved in the bond. Triple bonds are shorter than double bonds which are shorter than single bonds, given the bonds b...

MichaelMendozaD1F

how do we arrange bonds according to length?
I believe this was in the sampling hw Q11.

MichaelMendozaD1F

later in this problem it asks us for the oxidation number of chlorine, how do we find this? Hi, the sum of the oxidation numbers of the atoms in ion must equal the charge on the ion, -1. When oxygen is bonded to a nonmetal other than F, it has an oxidation number of -2. This is since there are four...

MichaelMendozaD1F

which sections of hw will be on the midterm? I do not recall if it is cumulative or not... I'm pretty sure I remember my TA say in discussion that the midterms are not cumulative, so the next midterm should be based on the end of the week 2/3/4 homework on the quantum realm and the week 5/6 homewor...

MichaelMendozaD1F

so how are we able to see which bonds are longer or smaller? like in Q11 of the sapling week 5 and 6 HW?

MichaelMendozaD1F

later in this problem it asks us for the oxidation number of chlorine, how do we find this?

MichaelMendozaD1F

Along with what everyone else has already said, a rough guideline for finding out if a bond is ionic or covalent is to find the difference in electronegativity between the two molecules. If the difference is greater than 2 then the bond is ionic, whereas if the difference is less than 1.5, the bond...

MichaelMendozaD1F

How do you classify if a compound is a Lewis acid or base when given the chemical formula?

MichaelMendozaD1F

Will we be expected to differentiate between compounds like this on the midterm?

MichaelMendozaD1F

Anh Trinh 1B wrote:
MichaelMendozaD1F wrote:when will the answers be reviewed or released?

Dr. Lavelle will not release the answers, but in his email he said that he'll be going over the problems that students had the most difficulty during his upcoming final exam review sessions in Week 10!

thank you!

MichaelMendozaD1F

thank you for being so positive even when we are low on energy for faith in ourselves

MichaelMendozaD1F

so this midterm will be more conceptual ?

MichaelMendozaD1F

essential oil on the neck and temples helps

MichaelMendozaD1F

which sections of hw will be on the midterm? I do not recall if it is cumulative or not...

MichaelMendozaD1F

when will the answers be reviewed or released?

MichaelMendozaD1F

I am under the impression they will be released next week?

MichaelMendozaD1F

When will our scores be released?

MichaelMendozaD1F

How are the points recorded?

MichaelMendozaD1F

hi, I finished this problem, but I had a question regarding the Na in the sodium hydroxide, where did it go? did we not include it in the ionic equation because it does not contain elements that formed the precipitate ? the products do not contain any Na molecules so I was curious as to where they w...

MichaelMendozaD1F

Hey, I believe Heisenberg will be there since it was covered on the modules. Things to know related to this: 1) There is an indeterminacy in smaller objects as their momentum and velocity is unknown when interacting with light. For an object like a baseball, we can determine their position and mome...

MichaelMendozaD1F

thank you! I was wondering the same thing since certain compounds are very tricky based on their placement and state of matter.

MichaelMendozaD1F

based off feedback from my TA and Lavelle, the best review will come from the fundamental problems in the syllabus. However, his modules should also help as they are audio visual with a assessment portion that will count as even further review. Good luck!

MichaelMendozaD1F

Compounds that can be used to store hydrogen in vehicles are being actively sought. One reaction being studied for hydrogen storage is Li3N(s) 1 2 H2(g) S LiNH2(s) 1 2 LiH(s). (a) What amount (in moles) of H2 is needed to react with 1.5 mg of Li3N? (b) Calculate the mass of Li3N that will produce 0....

MichaelMendozaD1F

Without using a calculator, estimate what amount of Br2 (in moles) can be obtained from 0.30 mol ClO2 in the reaction 6 ClO2(g) 1 2 BrF3(l) S 6 ClO2F(s) 1 Br2(l).

MichaelMendozaD1F

What is considered too small to calculate? 10^-38 and 10^-34 are too small to be measured yet 10^-10 is measurable. What is the cut off for detection?

MichaelMendozaD1F

I had trouble with this as well, as I submit all of my posts in one day, but today my posts had way less recorded. I hope this error will be fixed.

MichaelMendozaD1F

I believe this concept will not be fully addressed until a more advanced chem lesson, however, I do recall him mentioning it being all consuming. I expect it to be in Chem 14B or further.

MichaelMendozaD1F

I am also struggling with this topic in photoelectric effect, is there more review in the book? or is the sapling homework a better resource?

MichaelMendozaD1F

has there been an update about this requirement?

MichaelMendozaD1F

Is the requirement of a webcam determined by our TA? or is it mandated by DR. Lavelle?

MichaelMendozaD1F

what exactly does "transferable" unit mean in the statement "However very sensitive experiment would show smallest 'transferable' unit is one (discrete) H20 molecule".

MichaelMendozaD1F

E.17 Which sample in each of the following pairs contains the greater number of moles of atoms? (a) 75 g of indium or 80 g of tellurium; (b) 15.0 g of P or 15.0 g of S; (c) 7.36 3 1027 atoms of Ru or 7.36 3 1027 atoms of Fe.
(C in particular is becoming an issue for me)

MichaelMendozaD1F

I believe we will be provided a periodic table, or allowed one, for every midterm or exam in Chem 40A :) hope you are well!

MichaelMendozaD1F

E.23 Calculate the amount (in moles) of (a) Cu21 ions in 3.00 g of
CuBr;(b)SO moleculesin7.003102 mgofSO;(c)F2 ionsin 233
25.2 kg of UF6; (d) H2O in 2.00 g of Na2CO3?10H2O.
(I am confused as to why there are ions and what to convert them to if need be)

MichaelMendozaD1F

I was able to calculate the net moles of gas by adding the stoichiometric coefficients of the "reactants" side of the equation, which will be 30, and then did the same to the "products" side of the equation to get 36. I then got a difference of 6 by subtracting moles of reactant ...

MichaelMendozaD1F

E.9 Epsom salts consist of magnesium sulfate heptahydrate. Write its formula. (a) How many atoms of oxygen are in 5.15 g of Epsom salts? (b) How many formula units of the compound are present in 5.15 g? (c) How many moles of water molecules are in 5.15 g of Epsom salts? (most difficulty is stemming ...

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