CHEMISTRY COMMUNITY

Daniela_Chem14A

I am having difficulty understanding where we obtain Ka, when all we are given is the pH. Dr. Lavelle did an example during his review and we were able to figure out what Ka was because Kb was given, so we divided that by Kw (10^-14). But, there are problems that don't give you Kb. Either you are g...

Daniela_Chem14A

805070989 wrote:How do you know which chemical is the spectator in a equation? Are there certain qualities or signs that show it is a spectator?

You know which ion is the spectator because it will appear on both the reactant and product sides unchanged.

Ex. Na+......<=> Na+.....

Daniela_Chem14A

Harjot Manku 1C wrote:When doing calculations, do we always leave out the liquid and solid states?

Yes, because they don't affect the reaction. But, it's not that you are leaving them out, it's more that they are regarded as 1 and anything multiplied by 1 equals itself.

Daniela_Chem14A

I am confused about the bold NOTE in the end of the course reader on page 156, saying that: "if [H3O+] <10^-7, then solution is considered neutral because we know that autoprotolysis generates 10^-7 mol/L H3O+" In autoprotolysis two equal molecules transfer a proton between each other and...

Daniela_Chem14A

Alejandra Reyna 1E wrote:I am having a hard time distinguishing a lewis acid from a bronsted-lowry acid. Is there something to look for specifically when looking at chemical formulas?

A Bronsted acid is a proton donor and a Lewis Acid is an electron acceptor. H+ is usually involved with bronsted acids.

Daniela_Chem14A

sid bauer wrote:What is the significance of the % decomposition?

% composition helps you find moles of an element/compound that allows you to later find the empirical and molecular formulas of that compound.

Hope this help!

Daniela_Chem14A

Professor Lavelle went over a problem in class referring to ATP Hydrolysis. When we got our answer for the problem we got that ADP and P were equal to each other. My question is if the ratio of ADP and P were different rather than 1:1, would you have to multiply the different ratio to the value calc...

Daniela_Chem14A

It says to determine the formal charge of each atom. For part a. NO+, the answer book says: N has a charge of 0 O has a charge of +1 How do you find the charges of each atom? After drawing the lewis structure, you can see that the 5 initial electrons of N found through the periodic table minus the ...

Daniela_Chem14A

It's isoelectronic with fluorine, F-.

Daniela_Chem14A

Which atoms are more stable carrying a certain charge? Specifically which atoms are better off carrying a negative charge over a positive charge and vice versa etc.? Furthermore, just for verification, you would much rather have a molecule carry a formal charge of zero (for stability reasons) than ...

Daniela_Chem14A

Getting moles is a great start but, you have to find atoms and to do this you convert by using Avogrado's number.

Hope this help!

Daniela_Chem14A

I'm not really sure what you're exactly confused about but, I'm going to try to help as much as I possibly can. The first thing you should know is that the rows are numbered and those numbers are the coefficients of the orbitals of the elements. For example, the 1st row is numbered 1 so the elements...

Daniela_Chem14A

You are right about your inference on question 1. Your second question is a little confusing. When writing Ca and K configurations, d-block doesn't play a role. However, if what you were asking was for the configurations after Ca on the d-block, then you are right except for the configurations for ...

Daniela_Chem14A

E=hv ; v=frequency c=(lambda)v lambda= hc/E = [(Js)(m/s)]/J = m Plank's constant with (Joules)(seconds) , Js, cancels out with Energy that equals Joules (J). The seconds, s, cancels out with the s^-1 of speed of light. At the end you are left with meters, m, which, are the units you need to get for ...

Daniela_Chem14A

During the review session, Professor Lavelle showed the following example (also on the attachment): L-Dopa, a drug used for the treatment of Parkinson's disease is 54.82% of C, 5.62% of H, 7.10% of N and 32.46% of O and a molar mass of 197.19g/mol. My question is why does he multiply the percentage ...

Daniela_Chem14A

If the Electronegativity difference is between the range of 1.5<x<2, what will the bond be classified as? Is it even possible for the electronegativity difference to be between this range?

Guidelines: Ionic bond if x>2
Covalent bond if x<1.5

Thank you!

Daniela_Chem14A

You are right about your inference on question 1. Your second question is a little confusing. When writing Ca and K configurations, d-block doesn't play a role. However, if what you were asking was for the configurations after Ca on the d-block, then you are right except for the configurations for C...

Daniela_Chem14A

Sarah,

The question asked to find the mass of the product and you used the limiting reactant to do that, C6H9Cl3, how did you know to use C6H9Cl3 instead of AgNO3? I'm referring to the second line of your solution.

Thanks

Daniela_Chem14A

Sarah,

How did you know to compare C6H9Cl3 to AgCl rather than comparing AgNO3 to AgCl?

Thank you!

Daniela_Chem14A

You can tell that the limiting reactant is C6H9Cl3 by comparing the solutions. You need 0.012 moles of C6H9Cl3 but, from the chemical reaction, you are only getting 0.004 moles of C6H9Cl3, making it the limiting reactant. On the other hand, AgNO3 is the excess reactant because only 5.89 moles are ne...

Daniela_Chem14A

I'm not very familiar with how chem exams are structured so has anyone heard if Lavelle's Exams/tests are based solely on mathematical word problems or are they based on short answer problems such as definitions, explaining concepts/experiments, drawing models, etc. Thank you!

Daniela_Chem14A

In expressing our final answer, are we allowed to leave it as 0.0122 * 10^6 or do we have to write it as 1.22x10^4?

Daniela_Chem14A

Yes, you must always multiply in order to get whole numbers as your final answer because there is no such thing as fraction or decimals when writing Compound formulas' subscripts.

Daniela_Chem14A

From what I understood, Avogrado's number was based on the idea that a single atom of the Carbon isotope Carbon-12 has a mass of 1.99265x10^-23g. And since a mole refers to a dozen of something in this case a dozen of grams of carbon which equals 12g of carbon. They used these 12g of carbon and divi...

Daniela_Chem14A

I never took chemistry in high school so does anyone have any method that helps in going from Compound names to Compound formulas? Is there a list or something of the Compound names with their respective formulas that will be used in this course? Thank you.

Daniela_Chem14A

Zoe, I did the same thing as you but, like Chem Mod said there are 2 H. So you have to multiply by the ratio of 2 H for every 1 O. My final answer came out to be 3.78x10^24 atoms of H.

Daniela_Chem14A

I've been kicked out of the Chem A website. When I try going to it, it tells me that the website is password protected. Does anyone know the password it is asking for?

CHEMISTRY COMMUNITY

Search found 27 matches

Re: Ka

Re: Spectator

Re: Equilibrium

Re: Coursereader Pg 156

Re: Lewis vs Bronsted-Lowry Acids

Re: Decomposition

Equilibrium Concentration Calculations?

Re: #3.49

Re: Exam 1 question 5E

Re: Atoms and their Formal Charge

Re: Atoms

Re: Building up on electron configurations

Re: questions regarding e- configurations

Re: chapter 1 , question 23

Limiting Reactants?

Electronegativity difference?

Re: questions regarding e- configurations

Re: Limiting Reaction Question- Getting different answer

Re: Limiting Reaction Question- Getting different answer

Re: Limiting Reaction Question- Getting different answer

Exams/tests ?

Re: Fundamentals E.17

Re: Limiting Reaction Question- Getting different answer

Re: Avogadro's number

Compound Names to Compound Formula

Re: Self-Test E.1B [ENDORSED]

Chem A website problem?