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
SUMMARY

The discussion centers on calculating the number of oxygen atoms in 0.00334 grams of CaSO4·2H2O, with a molar mass of 172 g/mol. The calculation yields approximately 7.016 x 1019 oxygen atoms, derived from the formula: (0.00334 g / 172 g/mol) x 6 (oxygen atoms per formula unit) x 6.022 x 1023 (Avogadro's number). Participants noted slight variations in molar mass and results, suggesting potential discrepancies in quiz answer choices, indicating a possible typo in the provided options.

PREREQUISITES
  • Understanding of molar mass calculations
  • Familiarity with Avogadro's number (6.022 x 1023)
  • Basic knowledge of chemical formulas, specifically CaSO4·2H2O
  • Ability to perform scientific notation arithmetic
NEXT STEPS
  • Review molar mass calculations for hydrates
  • Learn about the significance of Avogadro's number in chemistry
  • Explore common errors in stoichiometric calculations
  • Investigate variations in periodic table values and their impact on calculations
USEFUL FOR

Chemistry students, educators preparing quizzes, and anyone interested in stoichiometry and chemical calculations.

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