Unit Quiz

Last week we took our weekly quiz for this unit and it went well. I got a grade that is lower than what I had hoped, but it was still higher than most of my other quizzes. After having got the quiz back, I release all of my little mistakes and where I went wrong. I will hopefully not make similar mistakes on the upcoming unit test. This unit seems like a lot of memorization, so maybe that is why I am doing better than many past units.

Rules for Placing Electrons

There are three basic rules for placing electrons. They are listed below:

1. Aufbau Principle: electrons enter orbitals of lowest energy first.
2. Pauli Exclusion Principle: an orbital can only contain two electrons with opposite spin.
3. Hund's Rule: within a sublevel, electrons enter singly before pairing up

Strong Acids and Bases

List of Strong Acids:                            monoprotic acids*

• Perchloric acid
• Chloric acid
• Hydrochloric acid*
• Hydrobromic acid*
• Hydriodic acid*
• Nitric acid 
• Sulfuric acid

Remember: Strong acids contain oxygens that outnumber the hydrogens by a ratio of 2 or more and protonate completely to produce H+ ions when placed in a solution.

Strong Bases:

    Strong bases are those that contain the hydroxide (OH-) ion plus a group one or two element. Just like strog acids, they dissocitate completely when placed in an aqueous solution. 

Helpful Links:

Identify Strong and Weak Acids and Bases Practice Quiz

Acids and Bases Practice Quiz

Determining pH and pOH

Use this box to go to and from hydriounium and hydroxide concentrations to pH and pOH. Just follow to arrows you need and use the functions on them. Examples are shown below.

Example 1

     What is the pH of a soultion that is 12.5 M HCl?

The problem gives us molarity of a strong acid, so that is the number we use for the [H+] concentration. We want to go from [H+] to pH, so we use the negative log function. 

-log[12.5]= -1.097

The substance has a pH of -1.097.

Example 2

What is the pH of a solution that has 8.95 M NaOH?

The problem gives us molarity of base, so we use this number for the [OH-] concentartion. This problem is a two step problem in which we can go from [H+] concentration to pH or pOH to pH. You will come out with the same answer either way.

Way 1:

Way 2:

Helpful links:

What is a Logarithm?
pH vs pOH

pH Scale

Pictured above is the pH scale. It is used to determine if a substance is an acid or a base. Substances with a pH less than 7 are acidic. Substances with a pH over 7 are considered basic. Substances with a pH of 7 are neutral. Remember, it is possible for a substance to have a pH less than 1 or greater than 14.

pH's of common substances

How to Tell if a Salt is Acidic or Basic

   When an acid- base reaction occurs, the products are a salt and water. The salt will be composed of the cation of the base and the anion of the acid. The determining factor of the strength of a salt is the strengths of the acid and base parents. Use the guide below to determine the strength of a salt.

Helpful Links:
Cation vs Anion

Weekly Quiz

The quiz over this unit was not so bad. I feel like I knew the material, but just made a few simple mistakes. It was only 18 questions so missing a few really put a dent in my quiz grade, but it was not completely terrible. One of the things that really helped me was that none of the options for the math questions included "none of the above". This way I could see if the answer I got was actually right instesad of being unsure if I got the right answer and it purposely was not listed or if I completely messed up the problem. This quiz gave me a chance to correct any mistakes I made in my calculations if I did not come out with any of the numbers listed. This unit does not seem that bad yet, but I have heard so much about how hard it is, so I am waiting for it to hit me.