Calculating Number of Oxygen Atoms in CaSO4: A Pop Quiz Challenge

  • Thread starter Thread starter nando94
  • Start date Start date
  • Tags Tags
    Atoms
Click For Summary

Discussion Overview

The discussion revolves around calculating the number of oxygen atoms in a given mass of calcium sulfate dihydrate (CaSO4·2H2O). Participants explore the arithmetic involved in the calculation, including the molar mass and the conversion to moles and atoms, while addressing discrepancies in their results.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant calculates the number of oxygen atoms in 0.00334 grams of CaSO4·2H2O, arriving at approximately 7.016 x 1019 atoms based on a molar mass of 172 g/mol.
  • Another participant suggests there may be a small arithmetic mistake and provides an alternative calculation resulting in 6.865 x 1019 atoms, noting a potential miscount in the molar mass.
  • A third participant proposes that differences in molar mass could arise from variations in periodic tables, indicating a molar mass of 172.171 g/mol and calculating 7.011 x 1019 oxygen atoms.
  • Participants discuss the answer choices provided in the quiz, suggesting that there may have been a typo given the closeness of their calculated results.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the correct molar mass and the resulting number of oxygen atoms, with no consensus on the exact values or the presence of a typo in the quiz answers.

Contextual Notes

Discrepancies in molar mass calculations and the potential for typographical errors in quiz answer choices are noted, but the discussion does not resolve these issues.

nando94
Messages
33
Reaction score
0
I had a multiple choice problem on my pop quiz. How many oxygen atoms are there in .00334 grams of CaS04 X 2H2O.

The molar mass is 172 g/mol. So .00334/172 = 1.9 x 10-5 moles x 6 since there are 6 oxygen x 6.022 x 1023 = 7.016 x 1019.

None of the answer choices had that. Did I do it wrong? I'm going to talk to my teacher about it tomorrow but its been bothering me lol.
 
Last edited:
Physics news on Phys.org
nando94 said:
I had a multiple choice problem on my pop quiz. How many oxygen atoms are there in .00334 grams of CaS04 X 2H2O.

The is 172 g/mol. So .00334/172 = 1.9 x 10-5 moles x 6 since there are 6 oxygen x 6.022 x 1023 = 7.016 x 1019.

None of the answer choices had that. Did I do it wrong? I'm going to talk to my teacher about it tomorrow but its been bothering me lol.

Some small arithmetical mistake? What is the nearest to yours among the answers? Yours seems to be close, I get 6.865 X 1019.

Oddly I get a slightly different molar, 175.5 mass from yours (miscounted H?) but anyway 1.9 X 10-5 moles. Your reasoning is correct so in that case, say it was an multiple choice exam you should go to the nearest to your number.
 
I think the slightly different molar mass is due to differences between periodic tables.

The answer choices were 2, 6, 5.41 x 10^22, 5.81 x10^22, 1.11 x 10^21. Since your answer was very close to mine, I'm thinking that there was a typo on the quiz. If I saw your answer among the ones above I would have picked it but they weren't even close. Hopefully it is a typo haha and thanks for the help!
 
I got:

molar mass - 172.171 g/mol

moles - 1.940×10-5

oxygen atoms - 7.011×1019
 

Similar threads

Help with Calculating Moles of Atoms in Chemistry Lab
  • · Replies 3 ·
Replies
3
Views
3K
Calculating Number of O2 and N2 molecules per m^3 of air
  • · Replies 8 ·
Replies
8
Views
8K