May 25, 2019, 03:41:41 PM
Forum Rules: Read This Before Posting

### Topic: Partial Mass Spectrum of Mystery Compound  (Read 484 times)

0 Members and 1 Guest are viewing this topic.

#### thehyruler

• Very New Member
• Posts: 1
• Mole Snacks: +0/-0
##### Partial Mass Spectrum of Mystery Compound
« on: February 26, 2019, 12:36:22 AM »
I started Yale's opencourse freshman organic chemistry course and I have a question on the first homework assignment found here: http://chem125-oyc.webspace.yale.edu/125/history99/2Pre1800/SPepysINewton/IsotopeMassSpec.htm

I understand the Pepys/Newton problem but I am confused as to how to determine the number of chlorine atoms there are using the Pepys/Newton problem. If you're unfamiliar, Pepys asked Newton what the probability of rolling one 4 using six tetrahedra versus two 4s using twelve tetrahedra versus three 4s using eighteen tetrahedra. But how do I apply that to determining the number of chlorine atoms there are when given these ratios?

Any help is much appreciated.

#### JacobAnderson

• Very New Member
• Posts: 1
• Mole Snacks: +0/-0
• Gender:
• I am Jacob Anderson. I am a professor
##### Re: Partial Mass Spectrum of Mystery Compound
« Reply #1 on: February 26, 2019, 10:17:29 AM »
I will see, if I can find anyone to help you.
Jacob Anderson
Head of Chemistry Department

#### AWK

• Retired Staff
• Sr. Member
• Posts: 6420
• Mole Snacks: +462/-79
• Gender:
##### Re: Partial Mass Spectrum of Mystery Compound
« Reply #2 on: February 26, 2019, 03:42:00 PM »
Check from 4 chlorine atoms up
or
recalculate abundance of 35-Cl to 1. Then Newton's binomial will be (1+x)n and n1n-1x easily will give you the number of chlorine atoms, even without a calculator (in the scale of the problem from the link you gave).
« Last Edit: February 26, 2019, 04:26:15 PM by AWK »
AWK