Mole & Avogadro Constant

University:
Cameron University
Course:
1364 | General Chemistry I
Academic year:

2024
Views:

15

Pages:

2
Author:

Kinsley Bowers

mole & Avogadro constant    The mole is the unit of measurement in the International System of Units (SI) for amount of substance. It has the unit symbol “mol”. Same as: [A dozen (doz) is a grouping of twelve entities.] Is analogous to saying: A mole is a grouping of 𝟔. 𝟎𝟐𝟐 × 𝟏𝟎𝟐𝟑 entities. Where: the Avogadro constant is: NA = 6.022 141 79 (30) x 1023 mol-1  By definition: A mole of It means:  12 6𝐶 has exactly 12 grams mass. 12 g of carbon-12 contains 𝟔. 𝟎𝟐𝟐 × 𝟏𝟎𝟐𝟑 atoms of carbon-12 By definition: 1 One “atomic mass unit” = 12 mass of one atom of Or: 1 atom of 12 6𝐶 12 6𝐶 weighs 12.000 amu, “u” Note about the mole: i.e. Glucose: 𝐶6 𝐻12 𝑂6     1 molecule of glucose contains 6 atoms of C, 12 atoms of H, and 6 atoms of O 1 mole of glucose contains 6 moles of C atoms, 12 moles of H atoms, and 6 moles of O atoms. 10 moles of glucose contains 60 moles of C, 120 moles of H, and 60 moles of O atoms. NA molecules of glucose contains 6 x NA atoms of C, 12 x NA atoms of H, and 6 x NA atoms of O. 1) What is the mass of 1 atom of carbon? We know: 1 mole  6.022 × 1023 carbon atoms  12 g of carbon-12 𝑚𝑎𝑠𝑠 𝑜𝑓 1 𝑎𝑡𝑜𝑚 𝑐𝑎𝑟𝑏𝑜𝑛 = 12 𝑔 = 1.993 × 10−23 𝑔 6.022 × 1023 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}. 1 𝑚𝑜𝑙 5.6 𝑔 × 55,85 𝑔 = 0.10 𝑚𝑜𝑙 0.10 𝑚𝑜𝑙 × 6.022×1023 𝑎𝑡𝑜𝑚𝑠 1 𝑚𝑜𝑙 = 6.04 × 1022 𝐹𝑒 𝑎𝑡𝑜𝑚𝑠 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. 𝑚𝑎𝑠𝑠 10.0 𝑚𝑜𝑙 = 𝑚𝑜𝑙𝑎𝑟 𝑚𝑎𝑠𝑠 = 55.85 = 0.1791 𝑚𝑜𝑙 of Fe mol of “S” = mol of “Fe” = 0.1791 mol 𝑚𝑎𝑠𝑠 = 𝑚𝑜𝑙 × 𝑚𝑜𝑙𝑎𝑟 𝑚𝑎𝑠𝑠 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑠𝑢𝑙𝑓𝑢𝑟 = 0.1891 × 32.06 = 5.74 𝑔 𝑠𝑢𝑙𝑓𝑢𝑟 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. 𝑚𝑜𝑙 = 𝑚𝑎𝑠𝑠 0.128 𝑔 = = 2.00 −6 𝑚𝑜𝑙 𝑚𝑜𝑙𝑎𝑟 𝑚𝑎𝑠𝑠 64000 𝑔/𝑚𝑜𝑙 2.00 × 10−6 𝑚𝑜𝑙 𝐻𝑒𝑚𝑜𝑔𝑙𝑜𝑏𝑖𝑛 × 8.00 × 10−6 𝑚𝑜𝑙 × 4 𝑚𝑜𝑙 𝐹𝑒 = 8.00 × 10−6 𝑚𝑜𝑙𝑒𝑠 𝐹𝑒 1 𝑚𝑜𝑙 𝐻𝑒𝑚𝑜𝑔𝑙𝑜𝑏𝑖𝑛 6.022×1023 𝑎𝑡𝑜𝑚𝑠 1 𝑚𝑜𝑙 = 4.82 × 1018 𝐹𝑒 𝑎𝑡𝑜𝑚𝑠

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