1. Bring 2 bags tomorrow for a FREE 100 Daily Grade!
WARM UP
Don’t forget to bring a bag of CANDY this week for Extra Credit points on your TEST!
Bring 2 bags tomorrow for a FREE 100 Daily Grade!
Classify the following chemical reactions as either Synthesis, Combustion or Decomposition and explain WHY.
C6H12C6 + O2  CO2 + H2O
N2 + H2  NH3
KClO3  KCl + O2

2. Law of Conservation of Mass Lavoisier (1743-1794)
Coal is completely burned
100 g
100 g
START
END
What do you observe?
Q:Write down your observations.

3. Law of Conservation of Mass Lavoisier (1743-1794)
Coal is completely burned
100 g
100 g
A: Weight of jar & its contents remains the same. Mass is conserved
In a chemical reaction, matter is neither created nor destroyed, it is transformed into something else.

4. balanced mass Since matter can not be created or
destroyed, chemical reactions must be
__________ in terms of _________.
balanced
mass
The amount of mass you start with must
equal to the mass of the products:
Mass of Reactants  Mass of Products
100g total =
100g total

5. Quick Write:
Write the Law of Conservation of Mass in your own words. (2 minutes)

6. The mass on both sides of the arrow must be equal.
According to the law of conservation of mass, how much zinc was present in the zinc carbonate? + = +
256g
256g
REMEMBER !!!
The mass on both sides of the arrow must be equal.
A 40 g B 88 g C 104 g D 256 g
ANSWER: = 104g of Zn

7. CuCO3(s)  CuO(s) + CO2(g) 123.6 g 79.6 g ? g 44.0 g
According to the law of conservation of mass, how much carbon dioxide was present in the copper (II) carbonate?
CuCO3(s)  CuO(s) + CO2(g)
123.6 g
79.6 g
? g +
44.0 g
123.6g
123.6g
What are the reactants?
CuCO3
123.6 g
What is the mass of reactants?
Mass?
CuO & CO2
What are the products?
What is the mass of products?
79.6 g + CO2
Answer: – 79.6 = 44.0g of CO2

8. For the Previous Two Examples
You can set every Chemical Equation up like an Algebraic Equation and solve it for the variable. For instance this equation,
can be written algebraically using the masses given on the previous slide like below. Now you only have to solve for x!
123.6 [g] = 79.6 [g] x
Show the algebraic equation for your solutions to the previous 2 problems in your notes.
CuCO3(s)  CuO(s) + CO2(g)

9. Solve the follow problem in your IAN Notebook.
Practice
Solve the follow problem in your IAN Notebook.
If 50 grams of sodium (Na) react with chlorine (Cl2) to form 125 grams of salt (NaCl), how many grams of chlorine reacted?
2Na + Cl2  2NaCl

10. Solve the follow problem in your IAN Notebook.
Practice
Solve the follow problem in your IAN Notebook.
From a laboratory process, a student collects 28.0 g of hydrogen (H2) and g of oxygen (O2). How much water was originally involved in the process?
H2O  H2 + O2