Daily Post 30/4/12

On your blog describe how the following molecules stick to a positive surface. Describe two things: 1. How much do they stick in relation to each other, and 2. How is it aligned.

NH₃, BH₃, CH₄, CO, N₂, O₂, and CO₂.

(Image created by me)

As shown by the image, NH₃ and CO have a strong particle charge, and BH₃, CH₄, N₂, O₂, and CO₂ have a weak particle charge.

Also, list which molecules of this group you would expect to dissolve in water.

CO, NH₃

Daily Post 25/4/12

Draw / Explain pictures of hot air and cold air. Which one is more dense? Which one is moving faster?















(Images created by me)

Which one is more dense?
If pressure is held constant, hot air will have a larger volume than cold air. Assuming that there is the same amount of molecules of hot and cold air, the density of hot air will be less than the density of cold air. Density = kg/m3

Which is moving more?
Hot air is moving more than cold air because temperature acts like a speedometer. The higher the temperature, the faster the speed of the molecules.

Which is more dense: Dry air or Humid air? Why?

At the molecular level and at the same temperature, dry air is more dense than humid air because dry air contains heavier molecules. If one sample was taken of each air, both samples would have the same amount of molecules in them. The water molecules in the humid air would have replaced some of the nitrogen or oxygen molecules. As a result, humid air would be less dense because waters molecules are lighter than nitrogen and oxygen molecules.

Daily Post 13/4/12

The shapes of molecules are very important in their reactivity with the human body.  Post a 3D image of caffeine and cocaine and show how the shapes of these two molecules are quite similar.

Caffeine: C₈H₁₀N₄O₂

Cocaine: C₁₇H₂₁NO₄

Observation

From each chemical formula, each molecule uses the same type of atoms to create both molecules.

April 13

Daily Post 12/4/12

Energy content (density) of materials is a very important characteristic to meet our energy demands. Use thermodynamic concepts to rank the energy density of CNG (compressed natural gas), ethanol, gasoline and Li ion batteries.

                Material              MJ/Kg          MJ/L

1.       CNG                        53.6              9

2.       Gasoline                  47.2             34

3.       Ethanol                    30                24

4.       Li ion batteries          0.72             0.9-2.23

Source: http://en.wikipedia.org/wiki/Energy_density

Asprin

Place on your blog the answers and steps (process) to this student's aspirin lab questions from Organic Chemistry I:
   "I started with 2.0 g of salicylic acid and 5 g of acetic anhydride and I got 2.1 g of acetylsalicylic acid (aspirin).  What is my theoretical yield and my percent yield?"

	C7H6O3        +     C4H6O3        ->    C9H8O4       +  HC2H3O2
Grams	2.0g	5.0g	2.612g
Molar mass	138.12	102.09	180.15
Moles	.0145	.0490	.0145
Limiting reagent	x

2.0g of C₇H₆O₃  x         1 moles   _ =  .0145 moles of  C₇H₆O₃

                               138.12g

5.0g of C₄H₆O₃  x         1 moles   _ =  .0490 moles of  C₄H₆O₃

                               102.09g

.0145 moles of C₉H₈O₄  x      180.15g   _ =  2.612g of C₉H₈O₄

                                         Moles

Theoretical yield of C₉H₈O₄ is 2.612g

Percent yield is 2.1g / 2.612g x100 = 80.4%



March 23

Limiting Reagents

Today in class we discussed limiting reagents.  On your blog, describe the process you used to determine how many quarter pound hamburgers could be made.

To determine how many quarter pound hamburgers I could make, I used a recipe (unit converter) and an order list (supplies) to begin.  From there, I found the limiting factor by multiplying the recipe and the order list together.  Some of the ingredients on the recipe required more than one of that ingredient (2 pieces of cheese) to create a quarter pounder.  From the list I created, I looked for the smallest number and concluded that the lowest number was the limiting factor.

For the following reaction, determine which reagent is limiting and how much of the product can be made:

Begin with 8.5 g of hydrogen (H₂) and 40.2 g of oxygen (O₂).

Post you answer and process for solving this question.

	2H2                       +                     O2                       →                   2H2O
Grams	8.5g	40.2g	22.61g
Molar Mass	2.016	32.0	18
Moles	4.216	1.256	1.256
LR	2.11	1.256 x

8.5g of H₂  x          1 mole   _  = 4.216 moles of H₂

       2.016g

40.2g of O₂  x         1 mole   _  = 1.256 moles of O₂

         32.0g

The limiting reactant is Oxygen

1.256 moles of H₂O  x        18g   _ = 22.61g of H₂O

                                     Moles

Daily Post 29/2/12

On your blog post practical examples of the types of reactions we are studying in class.  Perhaps these are reactions related to your career interest, or just of interest!

Acid-Base reaction

HCl + NaOH -> H₂O + NaCl

The combination of Hydrochloric acid and Sodium Hydroxide can be useful when stomach acid levels are higher than normal and need to be equalized.

PPT reaction

2Al(OH)₃ + 3H₂SO₄ -> Al₂(SO₄)₃ + 6H₂O

I find this reaction interesting because the Aluminum Hydroxide purifies the water molecules.

REDOX reaction

Fe +2 H₂O -> Fe(OH)₂ + 2H

In this reaction, the iron is being oxidized by the water molecules to form rust. I can relate this reaction to winter driving because when the snow sticks to the car causing oxidation to occur.

Gas forming reaction

CH₄ + H₂O -> CO_(g) + H_{2 (g)}

The combination between methane and steam is used to produce hydrogen gas and carbon monoxide. I find this reaction interesting because hydrogen in gaseous form can be used for multiple applications. 

Examples to include: PPT, REDOX, gas forming, and acid-base. Post the balanced reaction and why it is of interest to you.