CompositionStoichiometry

Review: Rates of DecayStrontium-90 is one of the harmful radionuclides that result from nuclear fission explosions. It decays be byet emission with a half-life of 28 years. How long would it take for 99.0% of a given sample released in an atmospheric test of an atomic bomb to disintegrate?

Law of Definite CompositionDifferent samples of a pure compound always contain the same elements in the same proportion by massThis corresponds to atoms of these elements in fixed numerical ratios

Law of Multiple ProportionsWhen two elements, A and B, form more than one compound, the ratios of the masses of element B that combine with a given mass of element A in each of the compounds can be expressed by small whole numbers

Atomic WeightsWeighted average of the masses of the constituent isotopes if an element.Tells us the atomic masses of every known element.Lower number on periodic chart.How do we know what the values of these numbers are?

The MoleA number of atoms, ions, or molecules that is large enough to see and handle.A mole = number of thingsJust like a dozen = 12 thingsOne mole = 6.022 x 1023 thingsAvogadros number = 6.022 x 1023 Symbol for Avogadros number is NA.

The Mole How do we know when we have a mole?count it outweigh it outMolar mass - mass in grams numerically equal to the atomic weight of the element in grams.H has an atomic weight of 1.00794 g 1.00794 g of H atoms = 6.022 x 1023 H atomsMg has an atomic weight of 24.3050 g 24.3050 g of Mg atoms = 6.022 x 1023 Mg atoms

The MoleExample: Calculate the mass of a single Mg atom in grams to 3 significant figures.

The MoleExample: Calculate the mass of a single Mg atom, in grams, to 3 significant figures.

The MoleExample: Calculate the number of atoms in one-millionth of a gram of Mg to 3 significant figures.

The MoleExample: Calculate the number of atoms in one-millionth of a gram of Mg to 3 significant figures.

The MoleExample: How many atoms are contained in 1.67 moles of Mg?

The MoleExample: How many atoms are contained in 1.67 moles of Mg?

The MoleExample: How many moles of Mg atoms are present in 73.4 g of Mg?

The MoleExample: How many moles of Mg atoms are present in 73.4 g of Mg?

Formula Weights, Molecular Weights, and MolesHow do we calculate the molar mass of a compound?add atomic weights of each atomThe molar mass of propane, C3H8, is:

Formula Weights, Molecular Weights, and MolesThe molar mass of calcium nitrate, Ca(NO3)2 is:

Formula Weights, Molecular Weights, and Moles

Formula Weights, Molecular Weights, and MolesOne Mole ofContainsCl2 or70.90g6.022 x 1023 Cl2 molecules 2(6.022 x 1023 ) Cl atomsC3H8 or 44.11 g6.022 x 1023 C3H8 molecules 3 (6.022 x 1023 ) C atoms 8 (6.022 x 1023 ) H atoms

Formula Weights, Molecular Weights, and MolesExample: Calculate the number of C3H8 molecules in 74.6 g of propane.

Formula Weights, Molecular Weights, and MolesExample: Calculate the number of C3H8 molecules in 74.6 g of propane.

Formula Weights, Molecular Weights, and MolesExample: What is the mass of 10.0 billion propane molecules?

Formula Weights, Molecular Weights, and MolesExample: What is the mass of 10.0 billion propane molecules?

Formula Weights, Molecular Weights, and MolesExample: How many (a) moles, (b) molecules, and (c) oxygen atoms are contained in 60.0 g of ozone, O3? The layer of ozone in the stratosphere is very beneficial to life on earth.

Formula Weights, Molecular Weights, and MolesExample: How many (a) moles, (b) molecules, and (c) oxygen atoms are contained in 60.0 g of ozone, O3? The layer of ozone in the stratosphere is very beneficial to life on earth. (a)

Formula Weights, Molecular Weights, and MolesExample: How many (a) moles, (b) molecules, and (c) oxygen atoms are contained in 60.0 g of ozone, O3? The layer of ozone in the stratosphere is very beneficial to life on earth. (b)

Formula Weights, Molecular Weights, and MolesExample: How many (a) moles, (b) molecules, and (c) oxygen atoms are contained in 60.0 g of ozone, O3? The layer of ozone in the stratosphere is very beneficial to life on earth. (c)

Formula Weights, Molecular Weights, and MolesExample: Calculate the number of O atoms in 26.5 g of Li2CO3.

Formula Weights, Molecular Weights, and MolesExample:Calculate the number of O atoms in 26.5 g of Li2CO3.

Formula Weights, Molecular Weights, and MolesOccasionally, we will use millimoles. Symbol - mmol1000 mmol = 1 molFor example: oxalic acid (COOH)2 1 mol = 90.04 g 1 mmol = 0.09004 g or 90.04 mg

Formula Weights, Molecular Weights, and MolesExample: Calculate the number of mmol in 0.234 g of oxalic acid, (COOH)2.

Formula Weights, Molecular Weights, and MolesExample: Calculate the number of mmol in 0.234 g of oxalic acid, (COOH)2.

Percent Composition and Formulas of Compounds% composition = mass of an individual element in a compound divided by the total mass of the compound x 100%Determine the percent composition of C in C3H8.

Percent Composition and Formulas of CompoundsWhat is the percent composition of H in C3H8?

Percent Composition and Formulas of CompoundsWhat is the percent composition of H in C3H8?

Percent Composition and Formulas of CompoundsExample: Calculate the percent composition of Fe2(SO4)3 to 3 significant figures.

Percent Composition and Formulas of CompoundsExample: Calculate the percent composition of Fe2(SO4)3 to 3 sig. fig.

151617182122252828293132323334383840404040404040414243444546474849