What is a mole in chemistry? What is Avogadro’s Number? The SI unit for measuring the The atomic mass of one atom of carbon-12 is 12 amu. ______Avogadro found that ______of carbon-12 had ______

atoms. The unit symbol is ______became

known as ______One mole is equal to ______which equals one mole! ______

That works for everything! Since particles of matter are so small, we can’t count them even if we could count that high. If we have one mole of calcium, how many atoms of calcium do we

have?

Moles are used to convert mass in

______to

______If we have 6.02x1023 atoms of

potassium, how many moles do we have?

Particles of Matter Particles of Matter continued Particles of Matter continued Formula Unit: Representative Atom: Representative particle of Molecule: Representative particle particle of ______of ______Formula units are described by Atoms are indicated by an Molecules are described by ______Examples: Examples: Examples: NaCl represents one formula unit of ______H O represents one water molecule 2 commonly called table salt.  How many H atoms?  How many atoms of Na?

 How many O atoms?  How many atoms of Cl?

 How many total atoms? Ion: Representative particle of  How many total atoms?

______

Na(HCO3) represents one formula ______C H O represents one sugar 12 22 11 unit of ______Ions are indicated by an molecule common name is baking soda. ______ How many C atoms?  How many Na atoms?

______ How many H atoms?  How many H atoms? Examples:

 How many O atoms?  How many C atoms?

 How many total atoms?  How many O atoms?

 How many total atoms?

How to Determine Molar Mass

Molar mass of an element is ______

______of the element from the periodic table, but the units are different.

The unit for molar mass is ______

 The molar mass of potassium is ______zinc is ______Oxygen can be rounded to ______

Molar mass of a compound requires a ______

______; this is often called formula

mass.

 The mass of ______in

the formula is ______together in the

ratios as of the ______; the

unit is in ______.

Let’s do examples inside using the mole map!

How are molecular and empirical formulas determined from a 3) Find the empirical formula of the compound by finding the ratio of the number of moles of elements. percent composition calculation?  Review: Empirical formulas are reduced versions of the  An empirical formula is a chemical formula with the lowest molecular formula. In a practical sense, this means that we should divide the number of moles of each element by the whole-number ratio of elements in a compound. smallest answer for number of moles. Since the smallest  A molecular formula is the actual chemical formula of a number is “7.14 moles”, we’ll divide both values by 7.14. compound. carbon: 7.14 ÷ 7.14 = 1  Empirical formulas are reduced versions of the molecular hydrogen: 14.3 ÷ 7.14 = 2 formula. For example, a compound that has an empirical formula of CH2O may have a molecular formula of C2H4O2,  Empirical formula: C3H6O3, C4H8O4, etc.  Handy hint: If the problem gives you the empirical Steps 1-3 for Calculating Empirical Formulas and Steps 4-5 for formula, you can start at the next step!

Calculating Molecular Formulas 4) Divide the molar mass of the compound in the problem by  Once you have a percent composition of a chemical compound, the molar mass of the empirical formula. it’s possible to figure out the molecular formula. Here’s how,  For our compound, the molar mass of the compound is using the example of a compound with a molar mass of 28

grams/mol in which the percent composition of the components  For the empirical formula, CH2, the molar mass is are as follows: o C: 85.7%  Divide as instructed in step 4 above o H: 14.3%

5) Multiply the subscripts in the empirical formula by the 1) Assume you have 100 grams of the chemical. This serves to number you found in step 4 to find the molecular formula. convert the percentages into grams.

In our example, we now have

NOTE: Sometimes the empirical formula and molecular formula are 2) Figure out how many moles of each element you have in the the same. compound.

What does the percent composition of a compound represent, and how is it calculated?

 The percent composition of a compound represents the percentage of each element in a compound by mass.

o  Percent composition is calculated by dividing the mass of a single element in one mole of a compound by the molar mass of the compound and multiplying by 100 to make a percentage. o Example using water, what is the percent composition of H and O?

o o H2 mass

o O mass