# Chemical Quantities.  Ways to measure matter:  Count how many of something you have  Weigh it (or mass it)  Volume Units that refer to a specific.

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Chemical Quantities

 Ways to measure matter:  Count how many of something you have  Weigh it (or mass it)  Volume Units that refer to a specific #  pair = 2  dozen = 12

 1 mole = 6.02 x 10 23 atoms, molecules, ions, formula units  A.k.a. Avogadro’s Number  1 mole of a substance contains 6.02 x 10 23 representative particles

Representative particle: refers to the species present in a substance: atoms, molecules, ions Substance Rep. Particle Formula R.P. in 1 mol Atomic N AtomN 6.02 * 10 23 Nitrogen Gas Molecule N2N2N2N2 6.02 * 10 23 WaterMolecule H2OH2OH2OH2O Calcium ion Ion Ca +2 6.02 * 10 23 Calcium flouride Formula unit CaF 2 6.02 * 10 23 SucroseMolecule C 12 H 22 O 11 6.02 * 10 23

 How big is one mole?  One mole of sand would cover L.A. to a depth of 600 meters (1,968 ft)  Marbles would cover the earth to a depth of 40 miles

 Propane is a gas used for cooking and heating. How many atoms are in 2.12 mol of propane (C 3 H 8 )?

 Atomic mass unit of all elements are based off the Carbon – 12 atom  The atomic mass of an element expressed in grams is the mass of a mole of the element  How many atoms are in one mole of magnesium?

 To calculate the molar mass of a compound, find the number of grams of each element in one mole of the compound. Then add the masses of the elements in the compound  What is the molar mass of CO 2

 Grams A 1 mole A = mole A gfm A  Mole B gfm B = gfm B 1 mole B conversions

 Avogadro’s Hypothesis – equal volumes of gases at the same temperature and pressure contain equal numbers of particles

 Standard temperature and pressure – (STP)  Standard temp: 0 o C pressure: 101.3 kPa or 1 atm @ STP 1 mole of gas occupies 22.4 L 22.4 L = molar volume of a gas @ STP

 END of Part 3

 Molar mass = density @ STP x molar volume @ STP  The density of a gas containing Carbon and Oxygen is found to be 1.946 g/L @ STP. What is the molar mass of the compound?

 The relative amounts of the elements in a compound are expressed as percent composition  The percent by mass of an element in a compound - the number of grams of the element divided by the mass in grams of the compound...multiplied by 100%.

 Calculate the percent composition of Carbon and Hydrogen in propane (C 3 H 8 ).

 Empirical formula: gives the lowest whole number ratio of the atoms of the elements in a compound What is the empirical formula of a compound that is 67.6% mercury, 10.8% sulfur and 21.6% oxygen?

 What is the empirical formula of a compound that is 25.9% nitrogen and 74.1% oxygen?

 END of Part 4

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