Place chapter 4 note card in the purple bin and copy weekly problem set.

 The AP Chem exam you will take on May 2 is a norm referenced exam. It is based off of how the whole sample of students do on the exam to determine if you pass it.  On average when a 60% on the AP chem exam is earned, a 5 is earned on the exam. 50% is a 4… and so on.  Original grades ranged from 64 to 32.5 %.  Curved grades were 100 to 65%.

 Over all well done  Points of concerns  Theory – needed to discuss the reaction and how to derive the formula from the mass by calculating moles, then using mole ratios  In the conclusion, you needed to state that you could check to see if your formula was correct by writing the formula by crossing and dropping the charges and reducing.

 I gave you all a break, as long as you attempted every problem you earned a 20/20.  Check all your answers

 Show demo of a light bulb in sugar and salt water.  Electrolyte  an aqueous solution with ions The ions create an electrical current to flow through the solution  Where do ions come from? Ionic compounds – metal and nonmetal  Where have you hear this term before?  Nonelectrolyte  A solution with no ions present – covalent compounds

 Ionic compounds in water  Ionic compounds dissociate into ions when it is dissolves  When the ions dissociate, water molecules surround around each ion, causing the ions to be hindered from recombining.  This allows the ions to freely move around uniformly in the solution  You can predict how the ions separate due to the charges. Examples: K 3 PO 4 and BaCl 2

 Molecule (covalent) compounds in water  When covalent compounds dissolve, the molecule stays intact.  Common molecular substances are acids  Exceptions: strong acids such as HCl ionize (ions dissociate)

 Types of electrolytes  Strong Electrolytes Nearly all the ions dissolved in solution Examples: NaCl, HCl Representing: HCl → H + + Cl - no tendency to recombine  Weak Electrolytes Very few ions dissolved in solution Examples: sugar (C 6 H 12 O 6 ), acetic acid (HC 2 H 3 O 2 ) Representing: HC 2 H 3 O 2 H + + C 2 H 3 O 2 - Tendency to recombine

 Precipitation Reactions  Occur when a solid forms  Example: potassium iodide and lead (II) nitrate solutions react. Write a balanced chemical equation.  Identify the precipitate formed (page 125)  Yes you have to memorize these

 Complete ionic equation:  Writes the equation in ions  Example:  Net ionic equations  An equation with the precipitate, liquid (usually water), or gas formed and the ions used to create the precipitate.  No spectator ions  Example:  Try Give it some thought on page 127

 Write a balanced chemical equation for BaCl 2 and K 2 SO 4. Cite the precipitate that is formed.  Write the complete ionic equation  Write the net ionic equation

 Review and complete practice exercises on page 125, 127, and 128. These answers are given, but the work is not. Make sure you show the work.  Page 157 #4.24  Modified directions: write a balanced chemical equation for each Identify the precipitate Write the complete ionic equation Write the net ionic equation