CELEBRITY CHEMIST of THE DAY

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CELEBRITY CHEMIST of THE DAY
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MOLE CONCEPT
Unit of measure for matter

• Number of particles in one mole Avogadros
  number 6.02 X 10 23
• 602 000 000 000 000 000 000 000

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How many molecules are present in 4 moles of H2O?
How many atoms are present?

• SOLUTION
• One mole of any substance contains 6.02 X 10 23
  particles, therefore
• (4 moles) 6.02 X 10 23 2.41 X 10 24 molecules
• mole
• Since there are 3 atoms per H2O molecule,
• the total number of atoms is
• (3 atoms) 2.41 X 10 24 molecules 7.23 X 10 24
  atoms
• molecule

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MOLAR MASS

• Mass of one mole mass of one atom/molecule
  expressed in grams rather than atomic mass unit
  (amu)
• 1 amu based on 1/12 the mass of C-12 (most
  common carbon isotope)
• Example
• 1 atom of He 4 amus
• 1 mole of He 4 grams
• 1 molecule of O2 2 x 16 amus/O 32 amus
• 1 mole of O2 32 grams

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FORMULA

• GIVEN WEIGHT
• MOLAR MASS

NUMBER OF MOLES

GW MM
n

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How many moles of carbon atoms are contained in 4
g of carbon?

• The atomic mass of carbon is 12 amu, therefore
  the molar mass of carbon is 12 grams.
• 4 g X 1 mole 0.333 mole C
• 12 g

CONVERSION FACTOR (from periodic table)
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2. How many moles of water are there in 36 g of
water?

• SOLUTION
• The molecular mass of H2O is 18 amu.
• The molar mass of H2O is 18 g.
• 36 g X 1 mole 2 moles H2O
• 18 g

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3. Calculate the mass of aluminum carbonate
(Al2(CO3)3) in 5.85 moles of the compound.

• In Al2(CO3)3 , there are 2 Al, 3 C and 9 O
• Formula mass (2 X 27 g/Al)
• (3 X 12 g/C) (9 X 16 g/O) 234 g
• Molar mass 234 g
• Mass of Al2(CO3)3 5.85 moles X 234 g 1369 g

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MOLAR VOLUME

• Volume of one mole of solid and liquids varies
  from one substance to another based on their
  density
• Example
• 1 mole of H2O (density 1.00 g/mL) has a mass
  of 18 grams and will therefore occupy 18 mL
• 1 mole of NaCl (density 2.165 g/mL) has a mass
  58 g
• (Na 23 g Cl 35 g) and would occupy a
  volume of 26.8 mL (58 g /2.165 g/mL)
• Volume of one mole of gas equal to 22.4 liters
  at standard temperature (0oC) and pressure (1 atm
  or 760 mm Hg) (STP)
• 1 mole of O2 gas 22.4 L at STP
• 1 mole of He 22.4 L at STP

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How many moles of nitrogen are present in 4.48
liters of nitrogen at STP?

• Since there are 22.4 liters of any gas at STP,
  the solution is
• 4.48 L X 1 mole 0.2 moles N2
• 22.4 L

CONVERSION FACTOR
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PERCENT COMPOSITION

• Percent by mass of each element present in the
  compound.

by mass of each element
Total mass of element X 100 Total mass of
compound

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What is the percentage composition of H2O?
H in H2O
2 X 1 g x 100 18 g
11.11

O in H2O
1 X 16 g x 100 18 g
88.89

TO CHECK 100.00