1. Chemical Reactions
Essential Unit 5

2. How did we describe chemical change?
A change in color
Production of a gas
Formation of a precipitate
How did we describe chemical change?

3. A representation of a chemical reaction in which the reactants and products are expressed as formulas.
Reactants  Products
Examples:
NaOH  Na+ + OH-
Mg(s) + 2HCl  Mg+ + H2(gas) + 2Cl-
Pb(NO3)2 + 2NaI  PbI(s) + Na2(NO3)2
Chemical Equations

4. Mass is neither created or destroyed in a chemical reaction.
Conservation of Mass

5. Chemical Equations
Whether you burn one carbon atom or six carbon atoms, the equation used to describe the reaction is always the same.

6. Chemical Equations
Whether you burn one carbon atom or six carbon atoms, the equation used to describe the reaction is always the same.

7. Chemical Equations
Whether you burn one carbon atom or six carbon atoms, the equation used to describe the reaction is always the same.

8. Conservation of Mass Balancing Equations H2 + O2  H2O

9. Conservation of Mass Balancing Equations Se+ + O2  SeO2

10. Conservation of Mass Balancing Equations HgO  Hg+ + O2

11. Conservation of Mass Balancing Equations Fe2O2 + H2  Fe2+ + H2O

12. Conservation of Mass Balancing Equations C6H12O6 + O2  CO2 + H2O

13. Avogadro’s Number 6.02 x 1023
Moles (mol)

14. Molar Mass Simply put, the mass of 1 mole of a substance
For an element, the molar mass is the same as its atomic mass (or atomic weight) expressed in grams.
The molar mass of carbon is grams.
The molar mass of sulfur is 32.1 grams.
Molar Mass

15. You calculate the molar mass of a compound by adding up the atomic masses of its component atoms and then expressing this sum in grams.
A carbon dioxide molecule is composed of one carbon atom (12.0 amu) and two oxygen atoms (2 × 16.0 amu = 32.0 amu).
Carbon dioxide has a molar mass of grams.
Counting with Moles

16. Suppose you have 55. 0 grams of CO2
Suppose you have 55.0 grams of CO2. To calculate how many moles of CO2 you have, multiply the mass by a conversion factor. You can check your answer.
Mole-Mass Conversion

17. Mole-Mass Conversion How many grams are in 1 mole of NaOH?
How many moles are in grams of NaCl?
How many grams are in 0.1 FeCl2?
How many moles are in 4.03 grams of MgO?
Mole-Mass Conversion

18. N H2  2NH3
How many moles of NH3 can be made if 7.5 moles of H2 react with enough nitrogen.
What mass of NH3 can be made from 35.0g of nitrogen?
Mole Ratios