Wednesday, September 30th

Sorry that I did not post the solutions to the homework assigned today. We will cover the problems briefly tomorrow, 10/1.

Friday, September 25th Part 2

Here is the solutions guide to the Chapter 4 Practice Test. Remember, Monday's test is 20 multiple choice questions.

Friday, September 25th Part 1

There was a request to see the solutions to problems 63, 65, and 66a. Here they are. 66 (a) and (b) are on an earlier post. (With problem 64 (a).)

Wednesday, September 23rd

Homework for tonight: page 184 problems 64, 66(b,c), 68. Solutions for these problems are posted.

The Hydrogen Peroxide Lab write up is due on Friday, 9/25. There will be a Check-Me-Quiz over the Hydrogen Peroxide Lab on Thursday, 9/24. All concepts from the lab are fair game. The grade for the CMQ will go in your lab section.

On Monday, 9/28 will be a 20 question, multiple choice test covering all material from Chapter 4. A practice exam was given out on Wednesday, 9/23. Answers to the practice exam are on the back page. I hope to have solutions to the problems posted on this blog prior to the weekend. Friday will be dedicated to reviewing for the exam.

Monday, September 21st

Attached are images or the following: 63 (c) of the homework set due today; all the slides from the Hydrogen Peroxide Analysis Lab.

Thursday, September 17th

Homework - Read pages 164 through 178. Pages 183-184 problems 58 (a-e), and 62 (a,b)

Wednesday, September 16th

We finished the Standardization / Unknown Molar Mass of an Acid lab today. Make sure that all calculations for the lab are complete and ready to turn in tomorrow. Also, solve problems 55 and 56 on page 183 of the book as part of the lab analysis.

From the previous homework assignment, the answers to question 51 are: [Na+1]=2.50M; [NO3-1]=.250M; [OH-1]=2.25M (Which makes the solution basic.); and [H+1]=0

For #52, [H+1] is limiting, thus the concentration is 0. [OH-1]=.020M. The resulting solution is basic.

For #53, [HCl]=.102M

Thursday, September 10th

Only homework is to read the Background and Pre-Lab sections of the Double Replacement / Ionic Reactions Lab. Please complete the one question in the Pre-Lab section. Also, within the Background section is a discussion on the concept of Ksp (Solubility Product). Ksp is the rating of how soluble a compound is. Any value that is less than 1 will not be soluble in water for our purposes. Thus, if you cannot determine if a compound is soluble, look at table A5.4 (on page A25 in the back of the book). Example: In class there was a debate on the solubility of lead (II) chromate (PbCrO4). Chromate is not included on the sheet of general solubility rules that was supplied to you. Another way to determine its solubility is to look up the Ksp value for lead (II) chromate. The Ksp value for PbCrO4 is 2 x 10^-16. This value is far less than one, thus the compound will not dissolve in water. We will explore the true use and meaning of Ksp next spring.

Wednesday, September 9

Above is an image of the solution for number 8 of the Common Ion, Precipitate, Concentration Worksheet. Let me point out a couple of key factors: (1) Chromate (CrO4(-2) is not on your solubility sheet. Remember, if you know that all alkali metals and ammonium are soluble and all nitrates are soluble, you can figure out precipitates by deductive reasoning. Thus, the precipitate has to occur between aluminum ion and chromate ion. (2) Hopefully the number of moles of each reactant is easy enough to work with to quickly determine limiting and excess reactants. There will be no limiting reactant left over, so that concentration will always be zero. What is left of the excess reactant will be divided by the total volume to find that concentration. Spectator ion concentrations are simply the mole values of each divided by the total volume. Problems 5 and 7 are very similiar to #8. Come and see me before class if you have any issues with the worksheet.

Tuesday, September 8th

I am doing this from memory at home without a book, so if I am wrong, don't kill me. Homework was pages 181-182, problems 13, 14, 15, 16, 21, 22, 23(a,b), 24(a,b), 25, 26. Bold problems were done in class. We had started 26 when time ran out. I will try and give some pointers to solve #26. The problem wanted to know the molarity of sodium ion [Na+1]. The brackets around the sodium ion symbol indicate concentration (molarity) of a particular species of compound or ion. There were two sources of sodium ion, sodium carbonate (Na2CO3) and sodium bicarbonate (NaHCO3). Each compound is soluble in water. Both compounds were given a molarity and volume, thus the moles of each compound can be found. Remember, for each sodium carbonate, there are two sodium ions. Thus the moles of sodium ion from sodium carbonate will be twice the moles of sodium carbonate. Once the moles of sodium ion are found from both sources, add them together and divide by the total volume when both solutions are added together. The concept of problem #26 will be a large concept tomorrow.

Tuesday, September 1st

Review for the Chapter 3 exam on Thursday. Below are the answers for the two AP Chemistry Test problems that we are using for review.

2008 Free Response

2a) We will discuss in class.

2bi) 1.848 g H2O-->0.1026 mol H2O

2bii) 1.630 g MgCl2-->0.01712 mol MgCl2

Empirical formula of the hydrate: (0.1026/0.01712)=5.993-->6 H2O
MgCl2*6H2O

2c) We will discuss in class.

2d) We will discuss in class.

2e) 5.48 g AgCl-->0.0191 mol MgCl2

2f) 0.0191 mol MgCl2-->1.82 g MgCl2-->61.1% MgCl2 by mass in the mixture

2005 Free Response

2ai) 0.5202 g C; 0.03771 g H; 0.1970 g O

2aii) Empirical Formula: (C3.5H3O)*2-->C7H6O2

2bii) Molar Mass = 122 g/mol

2c) We will discuss in class.

Monday, August 31st

Homework was pages 127-128 problems 96, 97, 98, 99, 100, 101, 102