Blog Week 30

On Monday, each group brought their cookies made with a different recipe. My recipe ended up being the real recipe. Other groups had too much of one ingredient or too little of an ingredient. This project was done, so we could understand what limited reactants and an excess reactant was. A limited reactant is a substance that is completely used up in a chemical reaction. An excess reactant is a substance that is partly used, after the chemical reaction there is still some of the reactant left over. On Tuesday, practiced with some problems on stoichiometry. First we balanced the equation, then we decided which reactant was limited and which one was excess. From there we figured out the ratio and continued with the problem doing the same steps from last week's lessons. Here's an example below:

               CH4 + 2O2 --> 2H2O + CO2  <-- need to balance equation

Before:   2.5xs   2.5LR        Ø           Ø     <--- Ø because it's being produced 

Change:  -1.25    -2.5        +2.5      +1.25 <-- are mols  

________________________________  <-- -1.25 bc it was a XS, and it was a 1:2 ratio, only 1/2 of 2.5 

After:        1.25      0          +2.4     +1.25

We also drew particle diagrams. I shows this chemical reaction in the picture below.

On Wednesday, we had a sub and we did more practice on limited and excess reactants. We also worked on converting moles into grams and grams into moles. 

Here are some examples:

3.

               2Al    +  3I2 --> 2AlI3  <-- need to balance equation

Before:   .50 xs  .72 LR      Ø       <--- Ø because it's being produced 

Change:  -.48    -.72        +.48      <-- are mols  

___________________________<-- -.48 bc it was a XS, and it was a 2:3 ratio, only 2/3 of .72

After:       .02       0          +.48     

4. Na2SO4 --> g    .20 mol--> g  Na2SO4 = .20 mols and molar mass = 142 

 .20 mol x 142g/1 mol = 28.4g 

On Thursday, we learned about yield percent. the equation for it is actual/theoretical. An example is 35g NaCl/50g NaCl = .7 = 70% 

We also worked on more examples like on Wednesday. Here is another example:

               2KCIO3  --> 2KCI + 3O2  <-- need to balance equation

Before:       1.2                0          Ø      <--- Ø because it's being produced 

Change:    -1.2           +1.8       +1.8    <-- are mols  

_____________________________  <-- -1.2 bc it's a 3:2 ratio, 3/2 of 1.8

After:          0              +1.8      +1.8

On Friday, I was absent. We were to take an assessment.