To Do… http://chem.illinois.edu Lab tomorrow. Read Chapter

13. Lon-Capa (HW2 Type 2 due

Wednesday, February 5 by 7 pm).

1

Polyatomic Ions Ammonium Nitrate Sulfate Hydroxide Phosphate Carbonate

2

The Mole Concept: Why?

We can count by weighing (relative masses).

Reactions occur by number of particles, we must deal with masses, so we must have a way of converting between number and mass.

Atoms/molecules are very small!

3

Calculate…You have 50.0 g of water.

How many moles of H2O molecules do you have?How many moles of hydrogen atoms are present in this sample?

4

Consider This…

Does a methane molecule (CH4) contain more hydrogen or more carbon?

5

Clicker QuestionDetermine the percent by mass of hydrogen in a sample of 2 moles of methane (CH4).

a) 12.57% by mass hydrogenb) 25.13% by mass hydrogen

c) 50.26% by mass hydrogend) I have no idea.

6

Clicker QuestionDetermine the percent by mass of hydrogen in a sample of 2 moles of methane (CH4).

a) 12.57% by mass hydrogenb) 25.13% by mass hydrogen

c) 50.26% by mass hydrogen

7

Calculate…

Determine the percent mass of oxygen in each of the following substances:

H2O (water)

H2O2 (hydrogen peroxide)

8

Determining a Formula You have some “nitrogen oxide”

compound and you want to figure out what it is (both the formula and the name). You know it’s 30.4% nitrogen by mass.

NxOy = formula?

name?

9

Calculate…

Determine the percent mass of nitrogen in:

dinitrogen tetroxide

10

Calculate…

Octane (a constituent of gasoline) is a hydrocarbon (consists only of carbon and hydrogen). It has a molar mass of about 114 g/mol and is 84.12% carbon by mass.

Determine the molecular formula for octane.

11

Calculate…You have equal masses of each of the following compounds:

Sulfuric acid: H2SO4

Sucrose (table sugar): C12H22O11

Potassium chlorate: KClO3

Which one has the greatest number of oxygen atoms?

12

Formulas for Ionic Compounds are Empirical Formulas

13