Stoichiometry Problems

Here is a picture of the notes we took/ the worksheet we did last week in class when we were beginning to learn about stoichiometry:

These practice problems, along with the flow chart at the top have been really helpful to me while studying this unit, and hopefully they will be to others too. Here is a website that I found to explain more in-depth how to do the above problems: Stoichiometry

Calculating Percent Yield of the Aspirin Lab

Recently in class, we dug out some old information from the Aspirin Lab we did a while ago, and used it to apply to this unit by calculating the percent yield of the reaction from the lab. The balanced chemical reaction that we began with was:

C7H6O3(s) + C4H6O3(aq) --> C9H8O4(s) + C2H4O2(aq)

If you don't know how to balance a chemical equation yet, here is a website to tell you how: Balancing Chemical Equations

Next, we used the mass of the starting salicylic acid to determine the theoretical amount of the acetylsalicylic acid formed, and got 6.7110g C9H8O4

Lastly, we determined the percent yield of the reaction by using this equation:

Source of above picture

Here is a website explaining how to calculate this: Percent Yield

When I used the above formula to calculate the percent yield of the aspirin lab, I came up with 77.179%. 

How to Find Limiting Reagent

When trying to find the limiting reagent in a chemical reaction, there are two different methods you can use. 

Method One:

1. Determine the balanced chemical equation for the chemical reaction.

2. Convert all given information into moles.

3. Calculate the mole ratio from the given information. Compare the calculated ratio to the actual ratio.

4. Use the amount of limiting reagent to calculate the amount of product produced.

5. If necessary, calculate how much is left in excess of the non-limiting reagent.

Method Two:

1. Balance the chemical equation for the chemical reaction.

2. Convert the given information into moles.

3. Use stoichiometry for each individual reactant to find the mass of product produced.

4. The reactant that produces a lesser amount of product is the limiting reagent.

5. The reactant that produces a larger amount of product is the excess reagent.

6. To find the amount of remaining excess reactant, subtract the mass of excess reagent consumed from the total mass of excess reagent given. 

Here is a website that I found that uses the above methods to work through several examples: Finding Limiting Reagent

Here is another website that has practice problems dealing with this topic: Limiting Reagent Practice Problems

Copper II Chloride and Iron Lab Reflection

For a couple days during this past week in class, we did the Copper II Chloride and Iron lab. It was by far one of the coolest labs we have done thus far. On day 1, we roughed up an iron nail with steel wool and put it in a baby food jar filled with water and Copper II Chloride. We then let it sit overnight. Here is what it looked like in the beginning:

Here is what it looked like after I checked in on it later that day, after the Copper had begun to form and the solution changed colors:

Here is what it looked like the next day, when we came back to the lab and a lot more Copper had been formed:

We took the nail out of the solution and look what had happened to it overnight:

I did not expect anything like this to happen to the nail so quickly! The lab is still ongoing, as we still have to go back next week and weigh the Copper that was made from the reaction. Overall, this lab was really cool, and calculating the amount of moles of each substance made and the percent yield was educational and really good practice. Here is a website that I found that tells you how to do this same experiment, but using lemon juice as your solution instead, so you can do it at home: Coating a Nail With Copper 

Activity Series of Metals Lab

This past Tuesday, we did a lab about determining an activity series. We combined several types of metals and acids to see if they reacted. A lot of them did, and produced things like bubbles and gas and sometimes changed colors! Here are a couple pictures of what some of the reactions looked like:

After we recorded all the reactions that occurred, we determined our own activity series for the metals, based off of which reacted with the greatest amount of things. Overall, this lab was the most interesting one that we have done so far. I really enjoyed seeing all of the different things that could happen during a chemical reaction.

Types of Reactions

Last week in class, we learned about several different types of reactions to prepare for the unit test that we took on Thursday. The type that we spent the longest time learning about were redox reactions. This stands for reduction and oxidation. During this type of reaction, electrons are transferred from a metal to a non-metal. If a species loses electrons, it is oxidized and is the reducing agent. If a species gains electrons, it is reduced and is the oxidizing agent. A trick to help remember this is: OIL RIG, which stands for "Oxidized is lost. Reduction is gained." A more specific type of redox reactions are redox single-replacement reactions. During these, the metals have changed places and "the likes attack like". This type of reaction is based on reactivity series. Here is a link to a website that I found that explains everything you need to know about redox reactions: Redox Reactions

Here are the other types of reactions that we learned about:

-Synthesis: two or more reactants combine to form one product
-Decomposition: one reactant produces two or more products
-Combustion: a hydrocarbon reacts with oxygen and the products are CO2 and H2O

Here is a picture of examples of synthesis reaction equations:

Source of above picture