CHEMISTRY COMMUNITY

Emilie_Paltrinieri_1K

So in general a weak base will raise the pH and a weak acid will lower the pH, right?
Yes, remember that acidic solutions have lower pH (so on the left side of the scale), while more basic solutions have higher pH (right side of the scale).

Emilie_Paltrinieri_1K

Does anyone know how many questions there will be in the final? and if the latest material will be covered the most, or if all the material will be equally distributed in the exam?

Emilie_Paltrinieri_1K

I would recommend first going over your notes, highlighting the most important concepts and formula. After you have reviewed the material, I would recommend doing as much practice problems as possible. You can do the problems assigned in the textbook as Dr. Lavelle has said that some of them may be ...

Emilie_Paltrinieri_1K

Acid rain is a very dangerous phenomenon that occurs through chemical reactions occurring in the atmosphere. When chemicals such as Carbon Dioxide (CO2), S02 and NO2 elevate in the atmosphere they react with water vapor and form acid rain. Water usually is neutral, being acid, it has a corrosive eff...

Emilie_Paltrinieri_1K

What are the main differences we should be looking for when recognizing acids or basis, looking at their formula and structure?

Emilie_Paltrinieri_1K

Does anyone have any helpful tips for remembering the rules when naming coordination compounds?

Emilie_Paltrinieri_1K

Emilie_Paltrinieri_1K wrote:I am getting an error, is this structure not correct?

I just realized I was missing a lone pair on the O!!

Emilie_Paltrinieri_1K

How can we determine whether a pi bond is delocalized? What does it mean?

Emilie_Paltrinieri_1K

I am getting an error, is this structure not correct?

Emilie_Paltrinieri_1K

Hi! I am having trouble uploading a screenshot in one of these texts. I tried both dragging the image in the message box and uploading it as a file, but nothing appears in the chat. Does anyone know how to help me?

Emilie_Paltrinieri_1K

Is a molecule that has a lone pair polar?

Emilie_Paltrinieri_1K

So is there a general rule to guide us in choosing a specific Lewis Structure for every molecule?

Emilie_Paltrinieri_1K

Yes it's cumulative, so everything starting from the beginning of the quarter!

Emilie_Paltrinieri_1K

I had a question regarding the VESPR model for Sulfite Ion, S03^2-. As Dr. Lavelle said, the lewis structure of the ion wasn't the most stable as it had a lone pair. The lone pair has then affected the angle at which the atoms lie, as they repel the bonding e- pairs more. However, if we would have d...

Emilie_Paltrinieri_1K

But a double bond would result in the same Formal charge of a single bond.
Fluorine: 7e-
Fc double bond= 7-(5+(4/2))=0
Fc single bond= 7-(6+(2/2))=0

Emilie_Paltrinieri_1K

This exercise is asking to draw the Lewis Structures of various molecules.
I was wondering why in the structure of ONF and NF2 we don't draw double bonds to pair all of the lone e- pairs that N has, but rather they keep a pair of loose e- on the N?

Emilie_Paltrinieri_1K

This exercise asks to predict the number of valence electrons for various ions.
For example, the ion Mn^4+, in the solutions manual has 3 valence e-.
Since valence e- are the ones in the outermost shell, shouldn't' the solution exclude the e- in 4s and just =1?

Emilie_Paltrinieri_1K

Yes, Lewis bases which are usually anions (who can therefore donate electrons) create coordinate covalent bonds when attached to the acid.

Emilie_Paltrinieri_1K

How can I determine if a molecule exhibits ONLY London (dispersion) forces?

Emilie_Paltrinieri_1K

I can't seem to find the correct answer for question 9, which is asking which lewis structures are best based on formal charge.
Could someone tell what steps I should follow to come to the right solution please?

Emilie_Paltrinieri_1K

I know there is a simple formula to find the Formula Charge of an atom, but I don't remember what it was. Could someone write it down for me?

Emilie_Paltrinieri_1K

What does it mean to have "ample" and "overwhelmingly" when talking about bonds in chemistry?

Emilie_Paltrinieri_1K

They are actually two different things.
Electronegativity describes how well an atom can attract electrons towards it.
Electron affinity represents the amount of energy released when an electron has been added to a atom/molecule, making it a negative ion.

Emilie_Paltrinieri_1K

These are the key steps when determining the lewis structure. Step 1: Determine the total number of valence electrons. Step 2: Write the skeleton structure of the molecule. Step 3: Use two valence electrons to form each bond in the skeleton structure. Step 4: Try to satisfy the octets of the atoms b...

Emilie_Paltrinieri_1K

Yes, you have identify which of the lewis structures in the picture has the lowest energy configuration. So consider the overall charge of the different structures

Emilie_Paltrinieri_1K

I was wondering whether we are able to view the solutions of the midterm in order to go over it?

Emilie_Paltrinieri_1K

Could someone tell me what the grading scale for Chemistry Community is? (Number of points, if it's on a weekly basis, ecc)

Emilie_Paltrinieri_1K

4s comes before 3d, remember what the Aufbau Principle states!

Emilie_Paltrinieri_1K

Does anyone know if there is a way to make the lectures available to view offline? Thank you so much!

Emilie_Paltrinieri_1K

Do we need to be able to find the electron density or is it something that will be given in the problems?

Emilie_Paltrinieri_1K

Hi! I was wondering whether we will have to be able to show the derivation of the equations we have studied, in particular of the De Broglie equation, in the midterm?

Emilie_Paltrinieri_1K

So what was the new equation that they found after doing the experiment of the photoelectric effect?

Emilie_Paltrinieri_1K

I would recommend watching the lectures and looking at the solved examples on the textbook to see how the problems function. After that, do the homework and ask for help if you don't understand some of the exercises!

Emilie_Paltrinieri_1K

Could someone please explain what are the values that quantum numbers can have in relation to one another? I haven't clearly understood what Lavelle explained during lecture regarding the value that each quantum number can have (ex. l=n-1, ecc)

Emilie_Paltrinieri_1K

What does a 2px state represent?

Emilie_Paltrinieri_1K

You can also use a second device you have! That would avoid spending extra money.

Emilie_Paltrinieri_1K

Hi! So for the midterm will we just need our laptop and an external camera? Is there something else we need (calculator, ecc)? or will it be provided in the respondus software

Emilie_Paltrinieri_1K

You should use whatever numbers is necessary to balance the equation and if in the end you have a fraction, you can multiply both sides by a different number so that the fraction becomes an integer.

Emilie_Paltrinieri_1K

I don't think sapling is mandatory, but I would recommend it as it is a great resource, as it gives another explanation of the material covered in class.

Emilie_Paltrinieri_1K

"King Henry Doesn't Usually Drink Chocolate Milk"

Emilie_Paltrinieri_1K

Does anyone know how the midterm exam will be structured? Like how many questions there will be and if the questions will all be exercises or if there can be some theory questions as well?

Emilie_Paltrinieri_1K

I think that if the question doesn't specify particular units of measurement, then both should be fine as they have equal values. Just remember to use the correct scientific notation nm= 10^-9
Also, round to the correct significant figures to not have any inconsistencies!

Emilie_Paltrinieri_1K

You can calculate the theoretical yield in problems as it is the value with the optimal efficiency of the experiment. But, in some cases, the actual yield doesn't match the theoretical yield as, for example, some solution can stick to the beaker.

Emilie_Paltrinieri_1K

Hi, I was just wondering whether the Post-assessment of the Audio Visual is graded and counts as HW or if just Sapling does?

Emilie_Paltrinieri_1K

When calculating the number of moles of an element we always use 100g. I was wondering if we use 100g just for semplicity, and if there is any particular case where we should consider different quantities.

Emilie_Paltrinieri_1K

I think we will have to understand, through the various rules, what significant figure is appropriate for the exercise given. Remember the different regarding zeros, decimal places and different approaches for subtraction/addition and multiplication/division.

Emilie_Paltrinieri_1K

I think the periodic table would be provided. I would recommend becoming familiar with all the information given in the table. For example, atomic mass, type of element, ecc

Emilie_Paltrinieri_1K

Hi, I am having trouble with question 6 of the week 1 homework.

This is what I did:
1) I calculated the molar mass of CuNO3= 63.546+14.001+3*(15.9994)=125.56g/mol
2) calculated the # of moles: 5.68/125.56= 0.045 mol
3) M=n/V--> V=n/M
V=0.045mol/0.440M=0.1L
V=100mL

Could someone please help me

Emilie_Paltrinieri_1K

Try rounding to 2 sig figs so that you won't have any decimal places, but just integers

Emilie_Paltrinieri_1K

2. Italy

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