CHEMISTRY COMMUNITY

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when given a table, you can use any reaction and the values to kind K, right?

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how do you know if it's zero order?

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what is the difference between the instantaneous rate and the unique rate law??

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how would i find the rate constant ????

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how would i find the rate constant ????

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Can someone help me figure this out: In 1972, grain treated with methyl mercury was released for human consumption in Iraq, resulting in 459 deaths. The half-life of methyl mercury in body tissues is 70. d. How many days are required for the amount of methyl mercury to drop to 10.% of the original v...

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so my question here is why does the book not have the k in front of [A](not) and Dr.Lavelle did put the K in front. Can someone please help.

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During lecture, Dr.Lavelle said that the rate law was

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just look at the coefficient and the way that the question is being asked.

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this would be whatever we get for m and n added together. Like the last example we saw during class on Friday.

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Okay, so for Test 2, it had us put the redox molecules from increasing order, how would we do that?

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hello, i was wondering, when you are doing the cell diagram, when do you know that you are supposed to add Pt on both sides????

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So for all of the past reactions, i have been putting the reactions on one side and the products on the other, when im done with the half reactions. So my question here is why does the answer in part e on the back of the textbook flip the answer and put Sn2+ on the reactant side and Sn4+ on the prod...

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because you use h20 to balance out the oxygens when the half reaction is not balanced

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how do you tell the difference between a cathode and an anode?????

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Im still confused on how to find out the moles. Do you set up the equation and then figure out how many electrons are used? I'm confused while doing the HW question 14.9 6th Edition

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can someone explain what the difference here is with an example, like if it goes from a +2 to a +4 what is it considered? oxidation or reduction???? I always get confused on how to know if its oxidation vs reduction.

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Also, in part b, how come when they balance the equation out, they get rid of Br2 and only write 6OH- --> 5Br-(aq)+BrO3-(aq)+3H2O(l) ???
how did they cancel out Br2??

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I'm also curious with this, what should I study?

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In adittion, how would you find out the oxidation number of an element??

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An isolated system means that no matter or heat can go into the system.

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does anyone know when Test 3 is???

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Does someone know when our final exam is??

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I have the same question.. sometimes they use C and sometimes they use K.. can someone clarify this for me please.

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Does anybody know if there is a practice midterm that Dr.Lavelle or any of the TAs/UAs provided?

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From past experience, his test tend to be conceptual. He wants you to really understand the concepts and know how to apply them. Also be able to denote when and how to use the formulas that he gives in class. The homework should be very similar to his test.

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A student added solid Na2O to a 200.0-mL volumetric flask, which was then filled with water, resulting in 200.0 mL of NaOH solution. 5.00 mL of the solution was then transferred to another volumetric flask and diluted to 500.0 mL. The pH of the diluted solution is 13.25. What is the concentration of...

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im not sure where you got 1.2*10^-7 if in the table it says the equilibrium constant is 1.0*10^-5

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Hey guys, I don't quite understand how to calculate K. It says to use Table 11.2 but it doesn't show the full equation.. can someone help me please. Here is the question: Use the information in Table 11.2 to determine the value of K at 300 K for the reaction 2 BrCl(g) + H2(g) --> Br2(g) + 2 HCl(g).

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I understand part C but can someone please explain part A and B

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why do we need to put -(pi)(d) (r^2)???? where does this formula come from????

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-x will always be on the reactant side, someone correct me if im wrong (:

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can someone explain this to me and when would we use it, thanks.

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How do you go from PH to Pka and vice versa?

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I am confused on 12.29d, e, and f... i totally forgot what to do when dilution and when it dissolves. Can someone explain to me please. The question states to calculate PH and POH d) 2.0 mL of 0.175 M KOH(aq) after dilution to .5000L e) 13.6 mg of NaOH dissolved in 0.350L of solution f) 75.0 mL of 3...

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PKw= POH+PH
PKa+PKb=14
PKa refers to acidity acid and PKb to weak basicity base

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So as I see here, maybe you can remember that the bases usually contain OH

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Did Professor Lavelle ever teach us how to determine the equilibrium if the temperature changes? Or would we just ignore the temperature and when he asks us about this, we would just answer it saying temperature affects equilibrium? I know that: When the reaction is endothermic, while forming produc...

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The Potassium, K, cancels on both sides which is why we don't write it on the equation. We only write NO2-

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can someone explain what a buffer is? I did not really understand this, thankyou.

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what does PV=nRT stand for???

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so when k=1, does that mean that there are the same amount of reactants and products????

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when calculating either K or Q, you always have to put [products]/[reactants]

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As mentioned by Lavelle, units do not matter because they will cancel out.

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I looked for the bond angles of the T-Shape but online some websites say slightly less than 90 degrees but others say 90 degrees and 120 degrees... someone help please

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We made a similar chart in discussion too. I want to point out that I believe our TA mentioned something about the angles being less than 109.5 in some cases, I'm not exactly sure why or in what instances, but I think he mentioned lone pairs. I also think Lavelle said that we don't have to know the...

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Assuming you are referring to hybridization in relation to chemical bonds, the following is a link to the first of a series of chemistry videos on hybridization and hybrid orbitals on Khan Academy: https://www.khanacademy.org/science/chemistry/chemical-bonds/copy-of-covalent-bonds/v/sp3-hybrid-orbi...

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I'm still a little confused on when a molecule is polar or not. So if the forces cancel out it is polar? The forces have to be facing each other right? (--><-- like that)

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I was watching a video on shapes and the guy kept saying angular.. is this the same thing as bent?

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How do you know when it is a seesaw shape? I get it confused with the tetrahedral shape :(

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So the more lone pairs you have, the more tight the molecule it is?

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Whats the difference between delocalized and localized pi bonds?

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I remember Dr.Lavelle discussing dipole moments and how the vectors of the molecules have to cancel in order to be polar. This week in discussion, my TA said something about the length in a vector, how would you know the length?

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How do you know if a molecule is a radical? And what is special about these?

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So as Dr. Lavelle said, shorter bonds are stronger and longer bonds are weaker, why is this? I get mixed up because he also talked about the angles in the bonds (shape of a molecule- ex: tetrahedral) why do they want to be as far away as possible??

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For this question I had trouble with part c. I have all the valence electrons down but I'm had trouble figuring out how to bond them. Where and how do I know what molecule goes with which one? Can someone give me hints or tips please, thanks.

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what does condensed phase refer to? I was unsure when Dr.Lavelle mentioned it in class???

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so I'm watching this tutorial on how to find the formal charge of a molecule and in the video it gives the equation as
formal charge = (# valence electrons in free atom) - (# valence electrons in bonded atom) is this right ??? or do we use the original equation given to us in lecture???

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So, Dr.Lavelle said that an element is highly polarizable if the electrons are highly distorted, does this make the ionic bond more or less with a covalent character? I remember him mentioning something about ionic bonds with covalent character... can someone explain how ionic and covalent bonds are...

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How do you know when an element is delta positive or delta negative??

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Hello, I was just wondering why is it that some elements have oxidation states - or +? Also, why is it that both - and + can exist for the same element?

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I never really understood what the xyz was on a shell?? Can someone clarify what this was referring to?

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So I'm still struggling with cations and anions.. so when its Na+ its a cation but can someone explain to me the difference in size? I remember something about the more protons, the smaller and the less protons, the bigger.. why is that???

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So I'm still struggling with cations and anions.. so when its Na+ its a cation but can someone explain to me the difference in size? I remember something about the more protons, the smaller and the less protons, the bigger.. why is that???

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For the midterm, I remember Dr.Lavelle said something on Friday about using all the numbers for Plank's constant (or any constant)... for example, instead of using 6.626, we would use all the numbers, which are 6.62607004... would we have to use all the numbers instead of just the first three.. beca...

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can someone explain the difference between cation and anion? How can I memorize it?

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Can someone help me memorize the way in which the orbitals goes from largest energy to lowest energy?
For example, 4s^1,4s^2 ... like how do i know when the orbital is full? also how do i read the periodic table.. like how would i know whats next when my orbitals are full and i have more electrons?

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I believe that moving from n=5 to n=3 is higher frequency because you are releasing energy

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What is the different between the orbitals?

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From the periodic table, can someone please explain why we can use [Ar] as Br and how do you do write it out, please and thanks

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c=(Lambda/wavelength)(velocity/frequency)
and
E=hv

I think that the basic equations that you need to know for test two are these, and from there you can play around with them based on what the question is asking (:

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I am not sure how to solve the question from the review test on our first quiz, can someone please help me Question: Hard water is water that has high mineral content (mainly Calcium and Magnesium). A concentration above 5.30 x 10−3 M is considered to be very hard water. Assuming that there are no m...

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I am a bit confused on how to use the equations provided by section G.
Can someone please explain what "c=n/V" and "n=m/M"?
Also, 1 M = 1 mol*L^-1, im a bit confused on what this means and how to use it in the formulas above.

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Yes, you would have to multiply the subscript by the parenthesis. The atoms in the parenthesis show you that you would only have to multiply the subscript by what is inside the parenthesis. It's like in math when you distribute a coefficient just that here, the coefficient is at the end of the paren...

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It would not make sense if you put a fraction as a coefficient
1) there can't be 4/5 of carbon, atoms can not be broken down
2) coefficients have to be whole numbers
In addition, if you were to think about it, using fractions will take up more time and the process will be longer.

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In the book, the questions asks "What volume of 1.25 x 10^-3 M C6H12O6 (aq) contains 1.44 umol (micro) of glucose molecules?" I am unsure how to change umol into mmmol. Can someone please explain these steps?

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