Rachel Maddiee Posted January 3, 2020 Posted January 3, 2020 Is this done correctly? mass = 27.8 g CaCI2 Number of CaCI2 in the compound = (unknown) Number of CI- ions in the compound = (unknown) Number of moles = mass/molar mass To find the number of moles of CaCI2 first you find the molar mass of the compound. 1 mole Ca x 40.08 g Ca/1 mole Ca = 40.08 g 1 mole CI x 30.45 g CI/1 mole CI = 30.45 g 1 mole CI x 30.45 g CI/1 mole CI = 30.45 g molar mass = (40.08 g + 35.45 g + 35.45 g) = 110.98 g/mol CaCI2 27.8 g CaCI2 x 1 mol CaCI2/110.98 g CaCI2 = 0.250 mol CaCI2 Now from equation No of Chloride ions are : 6.02 x 10^23 x 2 CI- ion = 1.204 x 10^23 CI- ions
Sensei Posted January 3, 2020 Posted January 3, 2020 38 minutes ago, Rachel Maddiee said: 1 mole CI x 30.45 g CI/1 mole CI = 30.45 g 1 mole CI x 30.45 g CI/1 mole CI = 30.45 g Incorrect. Typo. 39 minutes ago, Rachel Maddiee said: molar mass = (40.08 g + 35.45 g + 35.45 g) = 110.98 g/mol CaCI2 27.8 g CaCI2 x 1 mol CaCI2/110.98 g CaCI2 = 0.250 mol CaCI2 OK. 39 minutes ago, Rachel Maddiee said: Now from equation No of Chloride ions are : 6.02 x 10^23 x 2 CI- ion = 1.204 x 10^23 CI- ions Incorrect. 1
Rachel Maddiee Posted January 3, 2020 Author Posted January 3, 2020 I can’t find the typo? And can you please tell me more specifically what is incorrect? thank you!
Sensei Posted January 3, 2020 Posted January 3, 2020 11 minutes ago, Rachel Maddiee said: I can’t find the typo? And can you please tell me more specifically what is incorrect! In one line you entered the correct value, and one line later you entered wrong value.. Recheck them.
Rachel Maddiee Posted January 3, 2020 Author Posted January 3, 2020 (edited) mass = 27.8 g CaCI2 Number of CaCI2 in the compound = (unknown) Number of CI- ions in the compound = (unknown) Number of moles = mass/molar mass To find the number of moles of CaCI2 first you find the molar mass of the compound. 1 mole Ca x 40.08 g Ca/1 mole Ca = 40.08 g 1 mole CI x 35.45 g CI/1 mole CI = 35.45 g 1 mole CI x 35.45 g CI/1 mole CI = 35.45 g molar mass = (40.08 g + 35.45 g + 35.45 g) = 110.98 g/mol CaCI2 27.8 g CaCI2 x 1 mol CaCI2/110.98 g CaCI2 = 0.25 mol CaCI2 Now from equation No of Chloride ions are : 6.02 x 10^23 x 2 CI- ion = 1.204 x 10^24 CI- ions How is that? Edited January 3, 2020 by Rachel Maddiee
Sensei Posted January 3, 2020 Posted January 3, 2020 54 minutes ago, Rachel Maddiee said: Now from equation No of Chloride ions are : 6.02 x 10^23 x 2 CI- ion = 1.204 x 10^24 CI- ions That's still wrong.. Actually wronger than previous..
Rachel Maddiee Posted January 3, 2020 Author Posted January 3, 2020 What am I doing incorrectly? Am I missing a step? OK I fixed it mass = 27.8 g CaCI2 Number of CaCI2 in the compound = (unknown) Number of CI- ions in the compound = (unknown) Number of moles = mass/molar mass To find the number of moles of CaCI2 first you find the molar mass of the compound. 1 mole Ca x 40.08 g Ca/1 mole Ca = 40.08 g 1 mole CI x 35.45 g CI/1 mole CI = 35.45 g 1 mole CI x 35.45 g CI/1 mole CI = 35.45 g molar mass = (40.08 g + 35.45 g + 35.45 g) = 110.98 g/mol CaCI2 27.8 g CaCI2 x 1 mol CaCI2/110.98 g CaCI2 = 0.250 mol CaCI2 0.250 mol CaCI2 x 6.02 x 10^23 formula units = 1.505 x 10^23 formula units CaCI2 1.505 x 10^23 x 2 CI- ions = 3.01 x 10^23 CI- ions 1
Sensei Posted January 4, 2020 Posted January 4, 2020 (edited) Generally good +1. 18 hours ago, Rachel Maddiee said: 27.8 g CaCI2 x 1 mol CaCI2/110.98 g CaCI2 = 0.250 mol CaCI2 With one yet another digit of precision it is 0.2505 mol 18 hours ago, Rachel Maddiee said: 0.250 mol CaCI2 x 6.02 x 10^23 formula units = 1.505 x 10^23 formula units CaCI2 1.505 x 10^23 x 2 CI- ions = 3.01 x 10^23 CI- ions With one more digit it will be 1.50852*10^23, and 3.017*10^23 But generally good answer. Edited January 4, 2020 by Sensei
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