1 xx 10^211×1021 molecules are removed from 280" mg"280 mg of carbon monoxide. Calculate the number of moles of carbon monoxide left? [Answer:8.4 xx 10^- 3" moles"8.4×103 moles]

2 Answers
Jun 13, 2018

Approximately 8.48.4 millimoles

Explanation:

Total moles of Carbon monoxide ("CO"CO) is

"n"_"Total" = (280 × 10^-3\ "g")/"28 g/mol" = 10^-2\ "mol"

Moles of "CO" removed is

"n"_"removed" = 1 × 10^21 cancel"molecules" × "1 mol"/(6.022 × 10^23 cancel"molecules")

color(white)("n"_"removed") = 1.66 × 10^-3\ "mol"

Moles of "CO" left is

"n"_"left" = "n"_"Total" - "n"_"removed"

color(white)("n"_"left") = 10^-2\ "mol" - (1.66 × 10^-3\ "mol")

color(white)("n"_"left") = (10 - 1.66) × 10^-3\ "mol"

color(white)("n"_"left") ≈ 8.4 × 10^-3\ "mol"

Jun 13, 2018

8,34*10^-3 moles

Explanation:

CO has a molecular mass of 28, so 280 mg are 10 millimoles.
10^21 molecules are 10^21/N_A =1.66*10^-3 moles,
Subtracting 1.66*10^-3 moles from 10*10^-3 moles gives 8.34*10^-3 moles