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May 6, 2016

Posts by lena

Total # Posts: 1,035

chemisty
Thanks :)
July 22, 2009

chemisty
oops sorry :S I meant Cromate. Potassium Dichromate. In a lab that I did I mixed 0.1 M K2CrO4 with 2 drops of NaOH and I added Ba(NO)2 until I noticed a color change. When I did this, the K2CrO4 which was initally yellow formed a white precipitate and on the top there was ...
July 22, 2009

chemisty
What would happen if you reacted potassium dicarbonate with HCL and NaOH?
July 22, 2009

Chem
Thank You :)
July 21, 2009

Chem
So is K2CrO4 the equillibrium concentration of CrO4-2 is high whereas in K2CrO7 the CrO4-2 equillibrium concentration is low?
July 21, 2009

Chem
One of my questions asks, when can you conclude about the relative equillibrium concentrations of CrO4^2- in each of the colutions 0.1 M K2Cr2O7 and 0.1 M K2CrO4? Im really confused by this question. Could someone clarify it for me? Thanks :)
July 21, 2009

Chem
Thank You :)
July 19, 2009

Chem
Ohh wow, what an awesome tip! Thank you so much. This was so confusing until now :D So for something like (losing heat) 2A + B <-> 2C delta H postive it would be 2A + B <-> 2C -heat the reaction would move right?
July 19, 2009

Chem
I dont understand the effect of temperature on a reaction. For exmaple: CO + 3H2 <-> CH4 + H2O deltaH= -230 KJ If there were an increase in temperature then the CH4 and H2O would have a harding time becoming the CO and H2 so therefore the reaction would move to the right...
July 19, 2009

Chemistry
Thank you :)
July 19, 2009

Chemistry
so for the Kc value it would change correct? I did this: Kc = [PCl3][Cl2]/[PCl5] = [0.30][0.12]/[0.72] = 0.05
July 19, 2009

Chemistry
OHHHH. OK! But the equllibriums for the rest is correct, right?
July 19, 2009

Chemistry
Divide what :S I actually guessed how to do this. Im not too sure what I did. How would I get the 0.72 for the equllibrium of PCl5?
July 19, 2009

Chemistry
Initially, 1.68 mol of PCl5(g) and 0.36 mol of PCl3(g) are in mixed in a 2.00 l container. It is later found that 1.44 mol of PCl5 are present when the system has reached equillibrium. Calculate the value of the equllibrium. This is what I did: Equation: PCl5(g) <--> ...
July 19, 2009

Chemistry
Ohh. I understand now. Thank you so much :)
July 19, 2009

Chemistry
I want to turn the 19.6 into 280 and in order to do that I must make the numerator larger and the numerator is the SO3 so therefore the reaction will move to the left?
July 19, 2009

Chemistry
is the 1000 k, 1000 kelvin? :S
July 19, 2009

Chemistry
that is the second part of the question; figuring out whether the reaction will move to the left or right. Im not too sure how to figure that out.
July 19, 2009

Chemistry
0.500 mol of SO2, 0.100 mol of O2 and 0.700 mol of SO3 re intorduced simutaneously into a 1.00 L vessel at 1000 K. For the equillibirum, 2SO2 (g) + O2(g) <---> 2SO3(g), the value of Kc at 1000K is 280. Show mathemtically that the mixture is NOT at equillibrium. This is ...
July 19, 2009

sci
are radiocarbon dating and carbon-14 dating the same thing?
July 19, 2009

Chem
Thank you :)
July 9, 2009

Chem
I dont understand how Rutherford's gold foil experiment proved that the positive charge of the atom had a very small volume in comparison to the whole atom. Could someone explain this to me please?
July 9, 2009

Chem
should I have 6 around every F? :S
July 8, 2009

Chem
Would the I have a lone pair?
July 8, 2009

Chem
oops, you`re right. Thanks :)
July 8, 2009

Chem
the molecular geometry would be a trigonal bipyramidal though, correct?
July 8, 2009

Chem
where is the lone pair? isn't iodine completely bonded to the fluorines?
July 8, 2009

Chem
IF5 would be not equal to 0 right?
July 8, 2009

Chem
Where would I use N/A ? If the molecule is polar then the sum would be not = 0 and if it isnt polr then the sum would be 0. Correct>?
July 8, 2009

Chem
Basically it gives me a formula like Ch3Cl and it says to draw the lewis structure and the VSEPR name. The it asks for the number of bonded atoms and number of lone pairs the molecule geometry, whether or not there are polar bonds, the sum of bond dipoles and whether the ...
July 8, 2009

Chem
There is this one question that akss for the sum of bond dipoles. I don't understand that at all. What is the question asking? I thought I was figuring out if the difference between the dipoles and if I got a 0 then the molecule would be non-polar and if I got anything ...
July 8, 2009

Chem
Ohh. Yes I do see that. Thanks :)
July 8, 2009

Chem
Ohhhh OK. Thank you :)
July 8, 2009

Chem
Why isnt the carbon negetive ?
July 8, 2009

Chem
For something that has 3 different elements how would I know which is positive and which is negetive? For exmaple HCN.
July 8, 2009

Chem
How do I know which part of a compund is negectivly charged and which side is positivly charged? In BH3 how would I know if the B is positivly charged or negetively charged? and for hydrogen?
July 8, 2009

Chem
Thank you :)
July 8, 2009

Chem
Ok. Thank you :)
July 8, 2009

Chem
Is a C-H bond polar or non-polar? Is a C-Cl bond polar or non-polar? I have different sources giving me different ranges. One says that anything with an electronegetivity of 0.5 or less is non-polar and I have anothre source saying anything 0.3 and less is non-polar. Which one...
July 8, 2009

chem
Thank you :)
July 8, 2009

chem
what does the delta mean?
July 8, 2009

chem
U have to show the partial charges and bond dipoles on my ;lewis structure of CH3Cl For the partial charges would I just have a negetive sign as the superscript of Cl and a positive sign and the superscript of C ? What exactly must I do to show bond dipoles? I didn't know ...
July 8, 2009

Chem
When you said "While a physical appearance of an element makes it easier to explain to beginning students the how and why of chemical reactions," do you mean there are rules set in place and exceptions but they aren't explained; as students we just accept them as...
July 7, 2009

Chem
What are some pros and cons for energy level diagrams and electron configuration diagrams? I was very long for elements like uranium and such but im not sure if those are the types of answers im supposed to be giving. Are there any flaws in the two methods (obvious con)?
July 7, 2009

Chem
Thank you :)
July 7, 2009

Chem
Is this a possible quantum number: 3,2,2,-1/2 This is my thikning: n=3 so therefore l = 0-2 so therefore ml could = 2 However, many of my classmates said it was impossible.
July 7, 2009

Chem
Thank you :)
July 7, 2009

Chem
What 4 quantum numbers describes one of the outermost electrons in a strontium atom in ground state? 5,0,0,1/2 Is my answer correct?
July 7, 2009

Chem
I finally understand it. Thank you so much!
July 7, 2009

Chem
When I said below I meant on the actually forum; the previous question I posted.
July 7, 2009

Chem
Thank you :) Could you also please answer the question below? I still don't understand it.
July 7, 2009

Chem
when I said configuration I meant electron configuration
July 7, 2009

Chem
Theres this one question in my homework that says that there is an unusual but actual condensed configuration and they said to write it. Which element are they referring to? :S
July 7, 2009

Chem
Thank you so much :)
July 7, 2009

Chem
So we are following the Aufbau Principle?
July 7, 2009

Chem
"But the half filled rule, and the one you apparently used to fill the s half way and the p orbitals half way, ARE FOR THE SAME ORBITAL" So the 2S and 2P are both in the second orbital so therefore there is no electron promotion?
July 7, 2009

Chem
My teacher was saying that its better for the shells to be half full rather than one being completely full and the other being not half full. He was referring to Hund's law. What do you think about this?
July 7, 2009

Chem
I was asked to fraw the energy level diagram for carbon. Carbon has 6 electrons so would the 2s and 2p orbitals both be half full? 1s = 2 electrons 2s= 1 electron 2p = 3 electrons
July 7, 2009

Chem
Ohhh.. OK. I understand. Thank you soo much for all your help today :)
July 6, 2009

Chem
A -> 3C The molar mass of A is 10.0g/mol If 2.0 grams of A reacts, how many moles of C will be produced? A -------------------> 3C m.mass= 10.0g/mol mass = 2.0 g moles = 2.0 g/10.0 g/mol =0.2 mol moles of c = 3 x 0.2 = 0.6 mol Did I do this correctly?
July 6, 2009

Chem
Thanks :)
July 6, 2009

Chem
Are the followinf true: atomic radii decreases from left to right, across a row atomic radii increases from top to bottom of a column
July 6, 2009

Chem
Thank you so much :)
July 6, 2009

Chem
mass = 4.550 g molar mass = 142.05 g/mol n= 0.032030975 mol c= 0.032030975/0.125 = 0.256 mol/L would I have 3 or 4 sig. digs? cause when I converted 125.0mL into 0.125 L I lost a sig dig;or should it be 0.1250 L?
July 6, 2009

Chem
As a part of a study to see whther just the chloride ion on NaCl accelerates the rusting of iron, a student decided to see whtjer iron rusted in a solution on Na2SO4. The solution was made by dissolving 4.550 g of Na2SO4 in water using 125.0 mL volumetric flask to adjust the ...
July 6, 2009

Chem
I did make a mistake on my calculator. Thanks a lot :)
July 6, 2009

Chem
volume = 322 mL temperature = 150 celcius pressure = 175 kPa mass = 0.448 Calculate the molar mass of the gas. First I converted volume to 0.332 L. Second I converted 150 celcius into 423 kelvin. PV = nRt (175)(0.322) = n(8.314)(423) n= 0.016022988 molar mass = 0.448/0....
July 6, 2009

Chem
Thanks :D
July 6, 2009

Chem
Thanks a lot DrBob :)
July 6, 2009

Chem
A tank car containing concentrated HCL (molarity 12.1) derails and spills exactly 1500 L of acid. Solid potassium hydroxide is required ot neutralize the spill. (a) Write a balanced chemical equation. HCl + KOH -> kCl + H2O (b) What is the molar ratio between acid and base...
July 6, 2009

Chem
I think I understand it now. They also said at STP. I didn't notice that at first. Thanks :)
July 6, 2009

Chem
One of my questions asks me to find the volume of neon gas. I thought neon didn't attach with other atoms because it had a full valence shell, how would it form into a gas? What would the formula be? N2, N3 ?
July 6, 2009

Chem
Thank you :) If I would have had something like 2.4 would I round it to 2 because of significant digits?
July 6, 2009

Chem
How many moles of hydrogen and oxygen are in 2 moles of water? water: h2o # of molecules = (6.022 x 10^23)(2)= 1.2044 x 10^23 # of hydrogen atoms = (1.2044 x 10^23)(2)= 2.4088 x 10^24 # of oxygen atoms = 1.2044 x 10^24 Did I do this correctly? What do I do about significant ...
July 6, 2009

Chem
Ohh.. thank you :)
July 6, 2009

Chem
Hg(CN) I don't know how to name this. I know that Hg is mercury and C is carbon and N is nitrogen.
July 6, 2009

Chem
Thank you :)
July 6, 2009

Chem
superscript:226 element:Z subscript:29 Whats does the subscript and superscript represent?
July 6, 2009

Chem
Thanks :)
July 6, 2009

Chem
Does electron affintity increase from left to right on the periodic table? And are there any trends for the groups?
July 6, 2009

Science/Careers
OK. Thank you soo much.
July 5, 2009

Science/Careers
I wanted to know how universities look at summer school courses. My guidance counseller told me that it dosen't matter whether the course you take is in (normal)school or summer school but others are saying that some universities dont accept it. Im taking a core grade 12 ...
July 5, 2009

Careers/Science
Thank you :)
July 5, 2009

Careers/Science
How long in the undergraduate program to get into PharmD? And are there any school thats allow you to go right into PharmD from highschool?
July 5, 2009

Careers/Science
After the PharmD program are you officially a pharmacist or is there more education you have to go through?
July 5, 2009

Math
We're learning something about transformations on the exponents of a function. For exmaple 2^x becomes 2^4(x-2)+2. Would this mean that the 2^x graph stretched vertically by a factor of 4, moved two units to the right and 2 units downwards?
June 19, 2009

English
thanks :)
June 18, 2009

English
Whats that word that means like twisting a story; like making it more exciting than it is; something like that.
June 18, 2009

v-t graph
is the slope of a p-t graph the velocity?
June 17, 2009

v-t graph
how do you convert a p-t graph into a v-t graph?
June 17, 2009

Greek Origins
Thank you sooo much!
June 9, 2009

Greek Origins
so Dies means time of light?
June 9, 2009

Greek Origins
Is there any word originated from greek that means something like day; I need something that symbolizes a time of light.
June 9, 2009

Greek Origins
From what greek word did the word 'day' originate from (day as in a day of the week)? and what does that greek word mean in greek? I`ve been searching around and I havent found anything :(
June 9, 2009

Math
planned to hatch 20 chicks a year* CORRECTION
June 7, 2009

Math
I don't think I am understanding this question. Question: A zoo started with 16 cranes and panned to hatch 20 chicks. A few birds were kept for breeding and the rest realeased into the wild. At the end of last year, a total of 136 cranes had spent some time in the zoo. If ...
June 7, 2009

Greek Origins
From where in the greek language did the word Night originate from?
June 5, 2009

Cars
What type of fuel does the cadillac cts take? premium or regular?
May 25, 2009

earth science
Thanks! This helped a lot :]
May 21, 2009

earth science
if the planet is really small [compared to others, like Pluto], does that mean it has no gravity? like, would you fly on Pluto because it's gravitational pull isn't as strong?
May 21, 2009

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