Quiz grade reaction and test preparation

On Wednesday, we received our Stoichiomety quiz grades back and I got a 100%. I was so relieved. My hard studying the night before paid off. Now, I am preparing for the unit exam. Below are a couple helpful links with practice quizzes and tests that will help me learn more about the subject. Hope you find these helpful!

Somerset Academy Practice Test

Glencoe Practice Quiz

Day 1 and 2 of Copper (II) Chloride and Iron Lab

On Thursday and Friday, my lab partner and I performed an experiment where we produced copper from an iron nail and copper(II) chloride. On day one, after we passed our pre-lab quiz, measured about 4 grams of copper(II) chloride, and placed it in a baby food jar. It was a vibrant blue. Next, we added 50 mL of distilled water to the jar and stirred it until it dissolved. We then placed an iron nail that had been polished with steel wool in the jar to sit overnight. Within in minutes it looked like this...

You can see that the copper immediately began to form. On Friday, we came back to the lab and found our baby food jar like this...

 In order to separate the copper from the rest of the solution, we pulled out the rest of the iron nail, washing off the remaining copper on the nail with distilled water back into the baby food jar. Then, we siphoned off the solution of iron (II) chloride into the sink, careful not to lose any of the copper the reaction produced. We then added hydrochloric acid to the baby food jar to wash the copper and also siphoned it off into the sink. Lastly, we washed the copper again with distilled water and siphoned off the water. Finally, we left the copper in the baby food jar and the nail on a paper towel to dry. We will finish measurements this week.

Limiting Reagent and Excess Reagant

On Monday, we learned how to find the limiting reagent and excess reagent in a chemical reaction. There are two approaches. I prefer to use approach two. Below are the steps:

When solving for the limiting reagent, you must convert both of the reactants in a chemical equation to one of the products, using moles. Whichever conversion results in a smaller product, that is the limiting reagent. It is the limiting reagent because once that reactant runs out, the reaction will end and the other reactant will be left in excess. After determining the limiting reagent, you know the other reactant is the excess reagent. You can figure out how much was left in excess by converting the amount of the product that resulted from the previous limiting reagent conversion back to the amount of the excess reagent. Once you discover how much reacted, you can then subtract that number from the original amount and you will know how much is left after the reaction ends. 

This picture show the reactants before and after the reaction, distinguishing which is the limiting reagent and what is leftover and alone as the excess reagent. 

http://www.mhhe.com/physsci/chemistry/chang7/ssg/chap03_9sg.html

Below is a link that explains limiting and excess reagents and another link with practice problems. 

Explanation

Practice Problems 

New Unit

On Friday, we began our new unit: Stoichiometry. Stoichiometry involves the relationship between the reactants and products in chemical equations. In the lecture, we balanced equations and followed a flow chart (the one below) to find the grams and moles of its different products and reactants.

 Here is a video that explains Stoichiometry and its significance and a link to where you can practice simple Stoichiometry problems.
Video
Practice

Classifications

There are three umbrellas of chemical reactions:

• Formation of a solid
• Formation of water
• Transfer of elections

In the formation of a solid, double replacement reactions take place. On the reactants side, both reactants must be aqueous. On the product side, one product is insoluble and one product is soluble. 

In the formation of water, a strong acid and a strong base must react in order to form water and a salt. If the acid and base are not strong, they will not split. Double replacement reactions also take place in this type of reaction. 

If the reaction does not fit into either of these categories, it is a redox reaction. There are four types of redox reactions: single replacement, synthesis, decomposition, and combustion. 

Here is a link to practice recognizing reactions: Classification Quiz

Transfer of Electrons: Redox notes

In class yesterday, we learned about redox reactions and the different types. In redox reactions, electrons are transferred from the metal to the nonmetal. If a species loses electrons, it is said to be oxidized, and it is the reducing agent. On the other hand, if a species gains electrons,it is said to be reduced, and it is the oxidizing agent. A way to remember this is:

http://www.chemguide.co.uk/inorganic/redox/definitions.html

In redox-single replacement reactions, the metals change particles and the driving force is the transfer of electrons. The reaction is based on a reactivity series. Something to remember is "like attacks like." So, a metal attacks a metal, and a nonmetal attacks nonmetals. Below is an example:

http://makahiki.kcc.hawaii.edu/chem/single_displ_rxn.html

Next, we practiced synthesis reactions. Synthesis reactions occur when two or more reactants combine to form one product. The general formula is A + B = AB. Decomposition reactions are the opposite, so one reactant produces two or more products. The general formula for decomposition reactions is AB = A + B.

Lastly, we reviewed combustion reactions as our last redox reaction. In a combustion reaction, the reactants always include water, and produce carbon dioxide and water. Below is an example: 

http://www.angelfire.com/un/sch3u1/combustion.html

Here are a couple videos that further explain redox reactions:

Tyler DeWitt

Bozeman Science

Reactions that form water notes

Today in chemistry class, we took notes over reactions that form water. These reactions include an acid and a base, and the driving force is the production of water. A salt is also produced. For example:

http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/acidbase.html

Acids can be strong or weak and bases can be strong or weak.

Strong acids:

• produce H+
• protonate completely 
• are strongest when oxygens outnumber the hydrogens by 2 or more
• HCl, HBr, HI

Strong bases:

• contain an -OH anion
• completely disassociate
• All group 1 and 2 metals cations plus an -OH anion are strongest

Weak acids and weak bases:

• do not protonate completely
• are not on the memorized list

Here is a link that further explains strong/weak acids and bases: ChemTeam

Here is a link to practice determining is an acid is strong or weak: about chemistry

Below is also a molecular, complete, and net force equation using strong acids and bases that we solved in class: