Chemical Quantities and The Mole Chapter 11 Chemical Quantities and The Mole

Counting and Weighing If one penny has a mass of 1.2 grams, how much would 5 pennies weigh? What mass would a million pennies have?

How Many Pennies? How would you be able to determine how many pennies are in the jar? What if I told you that each penny weighs approximately 1.2 grams and that the bottle without the pennies weighs 127 g and with the pennies weighs 1.52 kg How many pennies are in the bottle?

Counting and Weighing The mass of the pennies and jar is 1.52 kg x = 1520 g Pennies in jar minus the mass of the jar = mass of pennies 1520 g - 127 g = 1393 g 1393 g x = 1161 pennies 1000 g 1 kg 1 penny 1.2 g

Avogadro And The Mole The mole is just a conversion factor that allows us to accurately work with atoms and molecules. One mole of any substance contains 6.02 x 1023 units of that substance.

How You Measure How Much? You can measure mass, or volume, or you can count pieces. We measure mass in grams. We measure volume in liters. We count pieces in MOLES.

Moles Defined as the number of carbon atoms in exactly 12 grams of carbon-12. 1 mole is 6.02 x 1023 particles. Treat it like a very large dozen 6.02 x 1023 is called Avogadro’s number.

Representative Particles The smallest pieces of a substance. For a molecular compound it is a molecule. For an ionic compound it is a formula unit. For an element it is an atom.

Types of Questions How many oxygen atoms are in the following? CaCO3 Al2(SO4)3 How many ions are in the following? CaCl2 NaOH

Types of Questions How many molecules of CO2 are there in 4.56 moles of CO2 ? How many moles of water is 5.87 x 1022 molecules? How many atoms of carbon are there in 1.23 moles of C6H12O6 ? How many moles is 7.78 x 1024 formula units of MgCl2?

Measuring Moles Remember average atomic mass? The amu was one-twelfth the mass of a carbon 12 atom. Since the mole is the number of atoms in 12 grams of carbon-12, the atomic mass on the periodic table is also the mass of 1 mole of those atoms in grams.

Molar Mass The mass of 1 mole of an element in grams. 12.01 grams of carbon has the same number of pieces as 1.008 grams of hydrogen and 55.85 grams of iron. We can write this as 12.01 g C = 1 mole We can count things by weighing them.

Examples How much would 2.34 moles of carbon weigh? How many moles of magnesium are in 24.31 g of Mg? How many atoms of lithium are in 1.00 g of Li? How much would 3.45 x 1022 atoms of U weigh?

What About Compounds? in 1 mole of H2O molecules there are two moles of H atoms and 1 mole of O atoms To find the mass of one mole of a compound determine the moles of the individual elements contained Determine how much each element would weigh add them up

What About Compounds? What is the mass of one mole of CH4? 1 mole of C = 12.01 g 4 mole of H x 1.01 g = 4.04g 1 mole CH4 = 12.01 + 4.04 = 16.05g The Molar Mass of CH4 is 16.05g The mass of one mole of a molecular compound.

Molar Mass Ionic Compound How do you find the mass of one mole of an ionic compound? Calculated the same way as molecular compound before What is the Molar Mass of Fe2O3? 2 moles of Fe x 55.85 g = 111.7 g 3 moles of O x 16.00 g = 48.00 g Molar Mass = 111.70 g + 48.00 g = 159.7g

Molar Mass The generic term for the mass of one mole. The same as gram molecular mass, gram formula mass, and gram atomic mass.

Examples Calculate the molar mass of the following and tell me what type it is. Na2S N2O4 C Ca(NO3)2 C6H12O6 (NH4)3PO4

Finding Moles of Compounds Counting Pieces by Weighing Using Molar Mass Finding Moles of Compounds Counting Pieces by Weighing

Using Molar Mass We can find the mass ‘grams’ of 1 mole of atoms, ions, or molecules. We can make conversion factors from these. To change grams of a compound to moles of a compound.

For Example How many moles is 5.69 g of NaOH?

For Example How many moles is 5.69 g of NaOH?

For Example How many moles is 5.69 g of NaOH? need to change grams to moles

For Example How many moles is 5.69 g of NaOH? need to change grams to moles for NaOH

For Example How many moles is 5.69 g of NaOH? need to change grams to moles for NaOH 1mole Na = 22.99g 1 mol O = 16.00 g 1 mole of H = 1.01 g

For Example How many moles is 5.69 g of NaOH? need to change grams to moles for NaOH 1mole Na = 22.99g 1 mol O = 16.00 g 1 mole of H = 1.01 g 1 mole NaOH = 40.00 g

For Example How many moles is 5.69 g of NaOH? need to change grams to moles for NaOH 1mole Na = 22.99g 1 mol O = 16.00 g 1 mole of H = 1.01 g 1 mole NaOH = 40.00 g

For Example How many moles is 5.69 g of NaOH? need to change grams to moles for NaOH 1mole Na = 22.99g 1 mol O = 16.00 g 1 mole of H = 1.01 g 1 mole NaOH = 40.00 g

Examples How many moles is 4.56 g of CO2 ? How many grams is 9.87 moles of H2O? How many molecules in 6.8 g of CH4? 49 molecules of C6H12O6 weighs how much?

Percent Composition Like all percents Part x 100 % Whole Find the mass of each component, Divide by the total mass. Movie

Example Calculate the percent composition of a compound that is 29.0 g of Ag with 4.30 g of S.

Getting It From The Formula If we know the formula, assume you have 1 mole. Then you know the pieces and the whole.

Examples Calculate the percent composition of C2H4? Aluminum carbonate.

From Percentage to Formula Empirical Formula From Percentage to Formula

The Empirical Formula The lowest whole number ratio of elements in a compound. The molecular formula is the actual ratio of elements in a compound. The two can be the same. CH2 empirical formula C2H4 molecular formula C3H6 molecular formula H2O both

Calculating Empirical Just find the lowest whole number ratio C6H12O6 CH4N It is not just the ratio of atoms, it is also the ratio of moles of atoms. In 1 mole of CO2 there is 1 mole of carbon and 2 moles of oxygen. In one molecule of CO2 there is 1 atom of C and 2 atoms of O.

Calculating Empirical Means we can get ratio from percent composition. Assume you have a 100 g. The percentages become grams. Can turn grams to moles. Find lowest whole number ratio by dividing by the smallest.

Example Calculate the empirical formula of a compound composed of 38.67 % C, 16.22 % H, and 45.11 %N. Assume 100 g so… 38.67 g C x 1mole C = 3.220 mole C 12.01 g C 16.22 g H x 1mole H = 16.06 mole H 1.01 g H 45.11 g N x 1mole N = 3.220 mole N 14.01 g N

Example The ratio is 3.220 mole C = 1 mole C 3.220 mole N 1 mole N The ratio is 16.06 mole H = 5 mole H 3.220 mole N 1 mole N C1H5N1 A compound is 43.64 % P and 56.36 % O. What is the empirical formula? Caffeine is 49.48% C, 5.15% H, 28.87% N and 16.49% O. What is its empirical formula?

Empirical to Molecular Since the empirical formula is the lowest ratio the actual molecule would weigh more. By a whole number multiple. Divide the actual molar mass by the mass of one mole of the empirical formula. Caffeine has a molar mass of 194 g. what is its molecular formula?

Example A compound is known to be composed of 71.65 % Cl, 24.27% C and 4.07% H. Its molar mass is known (from gas density) to be 98.96 g. What is its molecular formula?

Gases and the Mole

Gases Many of the chemicals we deal with are gases. They are difficult to weigh. Need to know how many moles of gas we have. Two things effect the volume of a gas Temperature and pressure Compare at the same temp. and pressure.

Standard Temperature and Pressure 0ºC and 1 atm pressure abbreviated STP At STP 1 mole of gas occupies 22.4 L Called the molar volume Avagadro’s Hypothesis - at the same temperature and pressure equal volumes of gas have the same number of particles.

Examples What is the volume of 4.59 mole of CO2 gas at STP? How many moles is 5.67 L of O2 at STP? What is the volume of 8.8g of CH4 gas at STP?

Density of a Gas D = m /V for a gas the units will be g / L We can determine the density of any gas at STP if we know its formula. To find the density we need the mass and the volume. If you assume you have 1 mole than the mass is the molar mass (MM). At STP the volume is 22.4 L.

Examples Find the density of CO2 at STP. Find the density of CH4 at STP.

The Other Way Given the density, we can find the molar mass of the gas. Again, pretend you have a mole at STP, so V = 22.4 L. m = D x V m is the mass of 1 mole, since you have 22.4 L of the stuff. What is the molar mass of a gas with a density of 1.964 g/L? 2.86 g/L?

All The Things We Can Change

We Have Learned How To change moles to grams moles to atoms moles to formula units moles to molecules moles to liters of gas molecules to atoms formula units to atoms formula units to ions

Mass Moles

Mass MM Moles

Mass Volume MM Moles

Mass Volume 22.4 L MM Moles

Mass Volume 22.4 L MM Moles Representative Particles

Mass Volume 22.4 L MM Moles 6.02 x 1023 Representative Particles

Mass Volume 22.4 L MM Moles 6.02 x 1023 Representative Particles Atoms

Mass Volume Moles 6.02 x 1023 Representative Particles Ions Atoms MM Moles 6.02 x 1023 Representative Particles Ions Atoms