Announcements Lon Capa HW #4 has been opened. Lab this week!

Follow dress code.

What Does a Chemical Equation Tell Us? Formulas for reactants

(left side) Formulas for products

(right side) Relative amounts of reactants

and products Phase (sometimes)

What Does it Mean to be “Balanced”?

Same number of each type of atom on each side (Law of Conservation of Matter)

How Do We Balance Chemical Equations? Mainly trial and error (some

general strategies though) Make sure you have same number

of each type of atom on both sides of equation

Do not balance by changing the subscripts!

Balance the least complicated molecule LAST.

Clicker #1 Which of the following shows the correctly

balanced equation for this reaction:H2O2 → H2O + O2

A) 3 H2O2 → 3 H2O + O2

B) H2O2 → 2 H2O + O2

C) 2 H2O2 → 2 H2O + O2

D) H2O2 → H2O + O2

Clicker #2 Balance the following equation and

determine the sum of the coefficients:C2H5OH + O2 → CO2 + H2O

A) 4B) 5C) 8D) 9E) 10

Why wear safety equipment?

Supposed to be the combustion of ethanol…http://chem.illinois.edu/SABICstudio/101/safety.html

Clicker #3 What are the possible products?

AgNO3(aq) + KCl(aq) → ?

A) AgCl and KNO3

B) AgNO3 and KCl

C) AgK and NO3Cl

D) Any of the above could be the products.

Clicker #4 So what is true about KNO3?

A) KNO3 is aqueous (soluble) in all three reactions.

B) KNO3 is the solid in reactions 1 and 2 but not reaction 3.C) KNO3 is the solid in reaction 1 but not in

reactions 2 and 3.D) KNO3 is the solid in reaction 2 but not in

reactions 1 and 3E) KNO3 is the solid in reaction 3 but not in

reactions 1 and 2.

Solubility Rules (Page 172)

1. Most nitrate salts are soluble.2. Most salts of sodium, potassium, and

ammonium cations are soluble.3. Most chloride salts are soluble. Exceptions:

Ag+ and Pb2+.4. Most sulfate salts are soluble. Exceptions:

Ca2+, Ba2+, and Pb2+.5. Most hydroxide salts are only slightly

soluble. Soluble ones are: Na+, K+, and Ca2+.

6. Most sulfide, carbonate, and phosphate salts are only slightly soluble.

Precipitation Reactions Know how to use the solubility

rules (you will be given them on the exam).

Know how to write equations from reactants (ionic reactants).

Understand what solutions “look” like at a very magnified level.