# Chapter 10: Chemical Quantities

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Chapter 10: Chemical Quantities
The Mole

What is a mole? The SI unit that represents the amount of a substance that contains 6.02 x 1023 representative particles of that substance. What is Avogadro’s Number? The number of particles contained in one mole of a substance. 6.02 x 1023 particles 602,000,000,000,000,000,000,000

What is a Representative Particle?
Atom: The smallest particle of an element Molecule: Group of atoms joined together by covalent bonds Formula unit: Lowest ratio of elements in ionic bonds Particle: This word can be used for any of the above words

Atomic or Formula Mass Mass of one single representative particle of a substance Measured in atomic mass units (amu)

C 12.01 amu NaCl 22.99 amu + 35.45 amu = 58.44 amu H2O
How do you find Atomic or Formula Mass? Add up the amu for every part of the substance: Find the amu on the Periodic Table C 12.01 amu NaCl 22.99 amu amu = amu H2O (1.01 amu x 2) amu = 18.02 amu

Molar Mass C 12.01 amu = 12.01 g/mol NaCl 58.44 amu = 58.44 g/mol H2O
The mass of one mole of any substance Measured in grams/ mole Same as finding atomic mass, but change amu to grams. C 12.01 amu = g/mol NaCl 58.44 amu = g/mol H2O 18.02 amu = g/mol

Converting # of Particles to # of Moles
Formula: 1 mole 6.02 x 1023 particles # of moles = # of particles x

Sample Problem: How many moles of NaCl are in 3.01x1023 formula units of NaCl?

Converting # of Moles to # of Particles
Formula: 6.02 x 1023 particles 1 mole # of particles = # of moles x

Sample Problem: How many particles are in 3 moles of water?

Converting # of Moles to Mass
Formula: Molar mass (g) 1 mole Mass (g) = # of moles x

Sample Problem: What is the mass of 1 mole of LiOH?

Converting Mass to # of Moles
Formula: 1 mole Mass (g) # of moles = Mass (g) x

Sample Problem: How many moles of NaCl are in grams of NaCl?

Mole-Volume Relationship
Avogadro’s Hypothesis: At standard temperature and pressure (STP) 1 mole of any gas occupies the same volume. STP: 0oC and 1 atm

At STP, 1 mole or 6.02 x 1023 particles, of ANY gas, has a volume of 22.4 L.
22.4 L is called the molar volume of a gas.

Converting # of Moles of gas to Volume
Formula: 22.4 L 1 mole Volume of gas = moles of gas x

Sample Problem: What is the volume, in liters, of 0.60 mol of SO2 gas at STP?

Converting Volume of gas to Moles
Formula: 1 mole 22.4 L Moles of gas = volume of gas x

Sample Problem: If you collect 8.00 L of O2 gas, how many moles have you collected?

Calculating Molar Mass from Density
Formula: grams mole grams L 22.4 L 1 mole = Density Molar mass

Sample Problem: What is molar mass of a gas with a density of 2.86 g/L at STP?

Percent Composition of a Substance
Mass of element in the compound x Molar Mass of Compound

Sample Problem  Find the % composition of H and O in water