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Fall 2016 โ CH 6A mole & Avogadro constant Instructor: J.T.
๏ท The mole is the unit of measurement in the International System of Units (SI) for amount of substance. ๏ท It has the unit symbol โ molโ.
๏ท Same as: [ A dozen ( doz) is a grouping of twelve entities.] Is analogous to saying: A mole is a grouping of ๐. ๐๐๐ ร ๐๐๐๐^ entities.
Where: the Avogadro constant is: N A = 6.022 141 79 (30) x 10^23 mol-^1
๏ท By definition: A mole of 126 ๐ถ^ has exactly 12 grams mass.
It means: 12 g of carbon-12 contains ๐. ๐๐๐ ร ๐๐๐๐^ atoms of carbon- 12
๏ท By definition: One โatomic mass unitโ = 1 12 mass of one atom of^6 ๐ถ
12
Or: 1 atom of 126 ๐ถ^ weighs 12.000 amu, โuโ
1) What is the mass of 1 atom of carbon?
We know: 1 mole ๏บ 6. 022 ร 1023 carbon atoms ๏บ 12 g of carbon- 12
6. 022 ร 1023
= 1. 993 ร 10 โ^23 ๐
Note about the mole: i.e. Glucose: ๐ถ 6 ๐ป 12 ๐ 6
๏ท 1 molecule of glucose contains 6 atoms of C, 12 atoms of H, and 6 atoms of O ๏ท 1 mole of glucose contains 6 moles of C atoms, 12 moles of H atoms, and 6 moles of O atoms. ๏ท 10 moles of glucose contains 60 moles of C, 120 moles of H, and 60 moles of O atoms. ๏ท NA molecules of glucose contains 6 x NA atoms of C, 12 x NA atoms of H, and 6 x NA atoms of O.
Fall 2016 โ CH 6A mole & Avogadro constant Instructor: J.T.
2) How many moles of Fe are in 5.6 g Fe? How many Fe atoms are contained in the sample?
By definition we know: 1 mole of Fe is 55.85 g per mole {see the periodic table}.
5.6 ๐ ร
1 ๐๐๐ 55,85 ๐ = 0.10 ๐๐๐
0.10 ๐๐๐ ร
6.022ร10^23 ๐๐ก๐๐๐ 1 ๐๐๐ = 6.04 ร 10
3) What mass of sulfur contains the same number of moles as are in 10.0 g of Fe?
First: Find the number of moles of Fe.
๐๐๐ ๐ ๐๐๐๐๐ ๐๐๐ ๐ =^
55.85 = 0.1791 ๐๐๐^ of Fe
mol of โSโ = mol of โFeโ = 0.1791 mol
๐๐๐ ๐ = ๐๐๐ ร ๐๐๐๐๐ ๐๐๐ ๐
๐๐๐ ๐ ๐๐ ๐ ๐ข๐๐๐ข๐ = 0.1891 ร 32.06 = 5.74 ๐ ๐ ๐ข๐๐๐ข๐
4) Hemoglobin is the oxygen-carrying protein of most mammals. Each molecule of hemoglobin contains 4 atoms of iron. The molecular weight of hemoglobin is about 64000 g/mol. How many moles of iron are contained in 0.50 moles of hemoglobin? Calculate the number of iron atoms in 0.128 g of hemoglobin.
1 mole of hemoglobin contains 4 X (moles) of iron. 0.5 mole of hemoglobin contains 4 X (0.5 moles) of iron = 2.00 moles of iron.
= 2.00 โ6^ ๐๐๐
2.00 ร 10โ6^ ๐๐๐ ๐ป๐๐๐๐๐๐๐๐๐ ร
= 8.00 ร 10โ6^ ๐๐๐๐๐ ๐น๐
8.00 ร 10โ6^ ๐๐๐ ร
6.022ร10^23 ๐๐ก๐๐๐ 1 ๐๐๐ = 4.82 ร 10
