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Posted: October 16, 2008 06:44 pm  | |||||
      IRC Nickname: Matt|Multi Group: Emeritus Posts: 668 Member No.: 49 Joined: December 30, 2007 Total Events Attended: 12    | Yay Chemistry! Show work please. All problems from the 2 quizzes I have that are due this evening. Question 1 (10 points) What is the wavelength (nm) of the energy that corresponds to the transition from n = 4 to n = 7 in a hydrogen atom? Question 2 (10 points) What is the wavelength of light (nm) having a frequency of 7.41 x 1014 Hz? Question 3 (10 points) What is the wavelength (nm) of a photon with a kinetic energy of 6.74 x 10-19 J? Arrange the following set of ions in order of decreasing atomic radii. Al3+, Ga3+, Ca2+, Rb+, K+ Arrange the following elements in order of decreasing first ionization energy. Be, Ca, Cs, Mg, K a. Mg > Be > Ca > K > Cs b. Cs > K > Ca > Be > Mg c. Ca > Mg > Be > K > Cs d. Be > Mg > Ca > K > Cs e. Ca > Mg > Be > Cs > K Given the following hypothetical equations, 2A + B --> 3C + 2D H = -52.5kJ C --> B H = -71.8kJ 2E--> B H = -88.6kJ, what is the enthalpy change (kJ) for the following reaction? A --> D + 2E 10.6 g of ice at -2.6oC is added to 139 mL of water at 38.2oC. What is the final temperature (oC) of the mixture? -------------------- Born at sea, baptized in blood your fame will never die. Your Division is one of the best if not the best division in the history of American arms -Gen George S Patton on the 45th Infantry Division  | ||||
Posted: October 16, 2008 09:01 pm | |||||
 IRC Nickname: chip54321 Group: Emeritus Posts: 532 Member No.: 119 Joined: January 11, 2008 Total Events Attended: 197 | First 3 I don't know yet, but here's what i can do: Arrange the following set of ions in order of decreasing atomic radii. Al3+, Ga3+, Ca2+, Rb+, K+ Al, K, Ca, Ga, Rb Arrange the following elements in order of decreasing first ionization energy. Be, Ca, Cs, Mg, K a. Mg > Be > Ca > K > Cs <-this one b. Cs > K > Ca > Be > Mg c. Ca > Mg > Be > K > Cs d. Be > Mg > Ca > K > Cs e. Ca > Mg > Be > Cs > K Given the following hypothetical equations, 2A + B --> 3C + 2D H = -52.5kJ (times 3) C --> B H = -71.8kJ (times 3) (times -2)2E--> B H = -88.6kJ (times -2 as well) ____________________________ 2A + B ---> 3c + 2D H = -52.5kJ 3C --> 3B H = -215.4kJ 2B --> 4E H = 177.2kJ _______________________________ (halve) 2A --> 4E+2D H = -90.7kJ (halve too) A --> 2E + D H = -45.35kJ what is the enthalpy change (kJ) for the following reaction? A --> D + 2E 10.6 g of ice at -2.6oC is added to 139 mL of water at 38.2oC. What is the final temperature (oC) of the mixture? Don't know, sorry That's all I could do. Hope it helps. You might wanna double check it just in case. --------------------      | ||||
Posted: October 16, 2008 10:43 pm | |||||
 IRC Nickname: Matt|Georgio9 Group: Emeritus Posts: 706 Member No.: 94 Joined: January 3, 2008 Total Events Attended: 0 | The first three are are just things you plug into equations. I did this all last year. I'd help you out but I don't know the equations off the top of my head for them. the equation for  2 isC = (wave length)(frequency) where C is the speed of light. 3x10^8 m/s = (wave length)(7.41 x 10^14 Hz) wave length = 4.0485829 x 10 ^ -7 m --------------------   | ||||
Posted: October 16, 2008 10:57 pm | |||||
| IRC Nickname: Matt|Georgio9 Group: Emeritus Posts: 706 Member No.: 94 Joined: January 3, 2008 Total Events Attended: 0 | Ok for your last question, i don't have the constants but this is how you do it LEFT SIDE: q = mc(T2 - T1) right? Ok so thats your left side, that tells you what your final temperature of the water will be. m is the mass of the water, c is the heat capacity constant, T1 is your initial temperature (38C) and T2 is your new temperature. RIGHT SIDE: q = A + B + C q = mc(T) + mc(T2 - T1) + Hn where term A is the energy to raise the temperature from -2.6C to the 0C, the melting point. term B is the energy to raise the temp from 0 to the equilibrium temp of the water surrounding. Term C is energy required to change the ice to water (heat of fusion). Make the right side = left side and there you go. -------------------- | ||||
Posted: October 16, 2008 11:53 pm | |||||
 IRC Nickname: Angus0000 Group: Emeritus Posts: 705 Member No.: 572 Joined: May 3, 2008 Total Events Attended: 128 | You use a combination of a couple equations to get 1. First one is E= R(1/(ni)^2 - 1/(nf)^2) where R is the rydberg constant for hydrogen Then, to find the wavelength, you plug the value you got for E into E=hc/(wavelength) , where h is Planck's constant and c is the speed of light. From there, you can solve for the unknown value for wavelength. --------------------  | ||||
Posted: October 17, 2008 12:53 am | |||||
 IRC Nickname: Kiwi011 Group: Emeritus Posts: 3052 Member No.: 40 Joined: December 30, 2007 Total Events Attended: 21 | Sorry but I struggled long and hard for my B- in Chemistry......I forgot it all that summer too --------------------  | ||||
Posted: October 17, 2008 02:00 am | |||||
| IRC Nickname: Matt|Multi Group: Emeritus Posts: 668 Member No.: 49 Joined: December 30, 2007 Total Events Attended: 12 | So for clarification, I ended up getting all but the last problem on my own, just had to read the book (Which I had been neglecting to do) . Just took my midterm, think I did fairly well on it. -------------------- Born at sea, baptized in blood your fame will never die. Your Division is one of the best if not the best division in the history of American arms -Gen George S Patton on the 45th Infantry Division | ||||
Posted: October 17, 2008 11:29 pm | |||||
| IRC Nickname: Mangomaniac2 Group: Emeritus Posts: 536 Member No.: 70 Joined: December 31, 2007 Total Events Attended: 63 |
A midterm in october? I feel bad for you --------------------  | ||||
Posted: October 18, 2008 12:48 am | |||||
| IRC Nickname: Matt|Multi Group: Emeritus Posts: 668 Member No.: 49 Joined: December 30, 2007 Total Events Attended: 12 |
Yep. Midterms for all my classes are this week and next. Also, got an 80% on that chemistry test, was nowhere NEAR as hard as we thought it would be. -------------------- Born at sea, baptized in blood your fame will never die. Your Division is one of the best if not the best division in the history of American arms -Gen George S Patton on the 45th Infantry Division | ||||
Posted: October 19, 2008 12:52 am | |||||
| IRC Nickname: Matt|Georgio9 Group: Emeritus Posts: 706 Member No.: 94 Joined: January 3, 2008 Total Events Attended: 0 |
... all my midterms are in october lol. I had one last wednesday and two more this thursday and the other is on friday, which is my birthday....bastards second year is a row thats happened. Anyways its in the morning soooooooo i'm going to go to the engineering pub/bar afterwards lol. 19 = legal in Canada bish. -------------------- | ||||
Chem 1315 (Urgent)