Fall 2014 Quiz Prep

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Michael Lonsway 3O
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Fall 2014 Quiz Prep

Postby Michael Lonsway 3O » Thu Oct 06, 2016 7:47 am

An excited hydrogen atom emits light with a frequency of 1.14x10^14 Hz to reach energy level for which n=4. In what principle quantum level did the electron begin?

I got n=3 but the answer is n=6. I used the different variations of the Rydberg equation and haven't been able get the right answer.

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Re: Fall 2014 Quiz Prep

Postby Chem_Mod » Thu Oct 06, 2016 8:54 am

If you read the question carefully, you'll notice that it says the atom emits light; thus, the change in energy between the 2 principal quantum levels must be negative. Try solving the problem with this piece of information, and you'll get n=6 as your answer.

Michael Lonsway 3O
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Re: Fall 2014 Quiz Prep

Postby Michael Lonsway 3O » Thu Oct 06, 2016 12:10 pm

I put n=4 into n-initial and solved for n-final which allowed me to get n=6. I'm wondering why this worked because the problem asked for the quantum level where the electron began.

Amy_Shao_2D
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Re: Fall 2014 Quiz Prep

Postby Amy_Shao_2D » Fri Oct 07, 2016 4:21 pm

Michael Lonsway 4E wrote:I put n=4 into n-initial and solved for n-final which allowed me to get n=6. I'm wondering why this worked because the problem asked for the quantum level where the electron began.


You got the same answer cause you did +deltaE=initial-final, and the actual way is -deltaE=final-initial. Delta E is negative since the problem says the hydrogen atoms emit light, so they're losing energy. Hope that helps!

Diwana Lucero 3K
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Re: Fall 2014 Quiz Prep

Postby Diwana Lucero 3K » Fri Oct 07, 2016 10:22 pm

I'm also having trouble with this problem and I checked the answer for this, but I don't understand where the En= -2.178 x 10^-18 J came from in the explanation?

Michael Lonsway 3O
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Re: Fall 2014 Quiz Prep

Postby Michael Lonsway 3O » Sun Oct 09, 2016 1:28 pm

Thanks for the help! I made Delta E negative since the problem states that energy is emitted and was able to get the right answer.

Rosalva_Mejia_41
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Re: Fall 2014 Quiz Prep

Postby Rosalva_Mejia_41 » Sun Oct 09, 2016 1:33 pm

A problem asks for the energy of a photon emitted with a wavelength of 5.50x10^2. I multiplied it by plank's constant and got the answer. However, I don't understand why that is if the original equations is E= h x frequency, not wavelength.

Wang_Pong_Chan_1L
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Re: Fall 2014 Quiz Prep

Postby Wang_Pong_Chan_1L » Sun Oct 09, 2016 4:18 pm

In the Rydberg Equation, does n1 refer to the higher energy level or the lower energy level?

904605949
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Re: Fall 2014 Quiz Prep

Postby 904605949 » Sun Oct 09, 2016 4:55 pm

Is number 5 on Quiz 2014 a limiting reactant problem? And also do we have to do/turn in all three of the self-quizes or do we just turn in one? Please help

Pauline Tze 3B
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Re: Fall 2014 Quiz Prep

Postby Pauline Tze 3B » Sun Oct 09, 2016 10:44 pm

Wang_Pong_Chan_1L wrote:In the Rydberg Equation, does n1 refer to the higher energy level or the lower energy level?

n1 refers to the initial energy level. Whether it is the higher or lower one depends on the problem.

Pauline Tze 3B
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Re: Fall 2014 Quiz Prep

Postby Pauline Tze 3B » Sun Oct 09, 2016 10:54 pm

Rosalva_Mejia_41 wrote:A problem asks for the energy of a photon emitted with a wavelength of 5.50x10^2. I multiplied it by plank's constant and got the answer. However, I don't understand why that is if the original equations is E= h x frequency, not wavelength.


Hi! I'm not understand how you got the answer just by multiplying it by planck's constant because doing that produced 3.64 x 10^-31 which is incorrect.

For this problem you need both E=h x frequency and c= lambda x frequency. Since you're given wavelength, you need to manipulate c= lambda x frequency and plug it into E=h x frequency.
Hope that helps!!

Rosalva_Mejia_41
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Re: Fall 2014 Quiz Prep

Postby Rosalva_Mejia_41 » Wed Oct 12, 2016 4:59 pm

Yea that's what originally did but the workbook had a different answer. Probably a mistake. Thank you.


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