Chapter 10.1 The Mole: A Measurement of Matter The measurement of the amount of something is done by one of three different methods: by count, by mass, or by volume.  Ex. Soda, grapes, gas Practice problem 1 & 2 pg 289 Ex. 1 dozen = 12

Chapter 10 10.1 The Mole: A Measurement of Matter Chemist use a unit that is a specified unit of particles. This unit is called the mole. Ex. 1 dozen = 12   1 mole = 6.02 x 1023 representative particles Avagadro’s number is 6.02 x 1023 A mole of any substance contains Avogadro’s number of representative particles, or 6.02 x 1023 representative particles.

Representative particles- refers to what is present in a substance; usually atoms, molecules, or formula units When dealing with compounds representative particles are molecules. When dealing with elements representative particles are atoms.

Converting number of particles to moles: moles = representative particles X ___ _ 1 mole_________ 6.02 x 1023 representative particles

Converting moles to number of particles representative particles = moles x 6.02 X 1023 representative particles 1 mole

Remember the atomic mass of an element is expressed in atomic mass units (amu)   Therefore 100 carbon atoms are 12 times heavier than 100 hydrogen atoms The atomic mass of an element expressed in grams is the mass of a mole of the element. Molar mass- The mass of a mole of an element. Ex. Sulfur 32.06 amu Molar Mass = 32.1g

The mass of a mole of a compound To find the mass of a mole of a compound you must know the formula of the compound.   To calculate the molar mass of a compound, find the number of grams of each element in one mole of a compound. Then add the masses of the elements in the compound. Ex. C6 H 1206

Chapter 10- 10.2 Mole-Mass and Mole Volume Relationships Use the molar mass of an element or compound to convert between the mass of a substance and the mole of a substance.    Mass(grams) = Number of moles x mass(grams) 1 mole or Moles = mass(grams) x 1 mole Mass(grams) 

The Mole Volume Relationship Avagadro’s hypothesis - states the equal volumes of gases at the same temperature and pressure contain equal number of particles.   Standard Temperature and Pressure (STP) - a temperature of 0 degrees Celsius, and pressure of 101.3 kPa, or 1 atmosphere (atm) At STP, 1 mol or 6.02 x 1023 representative particles, of any gas occupies a volume of 22.4 L. Molar volume of a gas is the quantity 22.4 L.

Calculating Volume at STP Volume of gas = moles of gas x 22.4 L 1 mol   Calculating Molar mass from Density Grams = Grams x 22.4 L Mole L 1 mole

10.3 Percent Composition and Chemical Formulas Percent composition- The relative amount of the elements in a compound   The percent by mass of an element in a compound, is the number of grams of the element divided by the mass in grams of the compound, multiplied by 100% % mass of element = mass of element X 100 mass of compound

Percent Composition from the Chemical Formula % mass = mass of element in 1 mol compound X 100% Molar mass of compound

Empirical Formula Empirical formula- gives the lowest whole number ratio of the atoms of the elements in a compound. The empirical formula of a compound shows the smallest whole number ratio of the atoms in a compound. Ex. Sample problem pg. 310  

Molecular Formulas The molecular formula of a compound is either the same as its experimentally determined empirical formula, or it is a simple whole number multiple of its empirical formula.   Once the empirical formula is known, you can determine its molecular formula but you have to know the compounds molar mass Sample problem pg.312