## Quiz 1 Preparation Fall 2014 Question 10

Ryan McDonough 4E
Posts: 17
Joined: Fri Sep 25, 2015 3:00 am

### Quiz 1 Preparation Fall 2014 Question 10

In the workbook, I was doing the Quiz Preparation from Fall of 2014 and got confused on question 10. I looked to the answer section where the steps were laid out.

In the answer section, the second step was to use the Bohr equation for H-atom which is apparently En=-2.178*10^-18 J(Z^2/n^2). I tried looking through the book and the course reader for anything on Bohr and tried finding out where the -2.178*10^-18 number could've come from. Is this a constant or something like that that'll be given to us or does someone know where to find this number or the Bohr equation? Your help would be greatly appreciated.

Thank you.

Shawn Barman 3C
Posts: 18
Joined: Fri Sep 25, 2015 3:00 am

### Re: Quiz 1 Preparation Fall 2014 Question 10

The equation you are looking for is En=-hR/n^2. The number -2.178*10^-18 is what you get when you multiply h and R.

Therese Abely 3A
Posts: 21
Joined: Fri Sep 25, 2015 3:00 am

### Re: Quiz 1 Preparation Fall 2014 Question 10

This question really confused me too. I tried using the formula that we used in class instead of the one in the book (E=-hR/n^2) but I got a different answer than the correct one. However, I thought we were supposed to learn this formula over the one in the book. Does the equation work if you use the one from class or is just the one from the book correct?

Roshni Kumar 1E
Posts: 20
Joined: Fri Sep 25, 2015 3:00 am

### Re: Quiz 1 Preparation Fall 2014 Question 10

I believe we are supposed to use the equation we used in class.

Daniella Ching 4C
Posts: 20
Joined: Fri Sep 25, 2015 3:00 am

### Re: Quiz 1 Preparation Fall 2014 Question 10

I used the equation from class (E=-hR/n^2) and got the right answer using that, so either version should work. However, I did the second part slightly differently than the work shown on page 26 of the workbook. I calculated out the energy for n=4 first, using (E=-hR/n^2), then plugged in the $\Delta E$ and $E_{4}$ values into the equation, $\Delta E=E_{4}-E_{n}$. I then found the quantum level by plugging in the $E_{n}$ value into the (E=-hR/n^2) equation.
Hopefully that makes sense!