Lab 6D

Last class we did 6D, where we mixed NaCO3 and CaCl2 together. A double replacement reaction during the mixing process. Precipitate, salt (NaCl2) was formed. The liquid turned white and cloudy from transparent. We measured the mass of the filter paper. In day 2, which is tomorrow, we will weigh the filter paper again and see if the mass has changed since it has absorbed Calcium Carbonate.

-Catherine

Molarity Stoichiometry and Gas Stoichiometry

Molarity Stoichiometry

*Remember the Molarity Formula

Molarity = Moles/ Litres

There are three steps to complete when given a molarity calculation in stoichometry.

Step 1: Write a balanced equation

Step 2: Map the solution (find the route to get to the answer)

Step 3: Calculation

Example 1:

Given this chemical reaction, FeCl3 + Mg(SCN)2 à Fe(SCN)3 + MgCl2, how many moles of MgCl2 would be formed if 50.0ml of 0.200 M FeCl3 is reacted with sufficient Mg(SCN)2?

Step 1: Write a balanced equation

2FeCl3 + 3Mg(SCN)2 à 2Fe(SCN)3 + 3MgCl2

Step 3: Calculations

0.0500 L FeCl3 X 0.200 mole  = 0.0100 moles    ß Find the amount of moles in FeCl3

                               1L FeCl3

0.0100 moles FeCl3 X 3 mole MgCl2  = 0.0150 moles  ß convert moles of FeCl3 to

                                        2 mole FeCl3                                 moles of MgCl2

Answer: 0.0150 moles of MgCl2

Check out this youtube video for more problems on molarity and stoichiometry!

http://www.youtube.com/watch?v=n5TaI_XR3y4

Gas Stoichiometry

*Remember: One mole of gas = 22.4L at STP

Example 1:

Given the formula Zn + HCl à ZnCl2 + H2, at STP what volume of H2 gas would be produced from 21.2g of HCl?

Step 1: Balance the equation

Zn + 2HCl à ZnCl2 + H2

Step 2: Change grams of HCl to moles of HCl

               2.12g HCl X 1 mole = 0.0581 mol HCl

                                  36.5g HCl

            Convert moles of HCl to moles of H2

            0.0581 moles HCl X 1 H2  = 0.2904 mol H2

                                              2 HCl

            Convert the moles of H2 to the volume of H2

            0.02904 mol H2 X 22.4L  = 0.651L

                                          1 mole

Answer: 0.651 L

If you are still confused check out this Youtube Video!!
http://www.youtube.com/watch?v=9Bc7igjXfYU

But when in doubt follow your mole map!

Remember that you can convert between compounds or elements using the mole ratio!!!!

-Candace

Stoichiometry Calculations

(Moles, particles, atoms)

Ex:  How many grams of Ca are produced if there are 4.24 moles of HBr?

       1).  Balance the eq'n:    2Ca+2HBr--->2CaBr+1H2 
       2). Next make a road map:  4.24 mol HBr---> ?grams Ca
       3). Now do the calculation: 4.24 mol HBr x 1 mol Ca x 80.2g Ca  = 85g Ca.
                                                                        2 mol HBr   2 mol Ca


Try some practice problems:
1) How many moles of HCl are needed to produce .76 g of CaCl?
2) How many grams of Ca are needed to produce  1 molecule of H?
3) How many atoms of H will be formed when 3.42 moles of Cl are formed?
4) How many grams of CaCl are needed to form 8.19 moles of HCl?

Check out this link: http://www.youtube.com/watch?v=jVtP9VSrdGw&feature=related
If catchy songs help you study, then this link will do the trick.

-Lauren                                                                                                                              

Stoichiometry

What is Stoichiometry?
- it's the study of the relationship between the number of reactants needed to produce the product and the amount of product produced

What does it do?
- it allows us to find out the mole ratio in an equation
- mole ration tells us the ratio of the molecules or moles in a substance
- the numbers in the ratio = the numbers in front of the chemicals in a balanced equation

Sample questions that deal with Stoichiometry
1) 3NO₂ + H₂0 --> 2HNO₃ + NO
How many grams of nitrogen dioxide are required in this reaction to produce 5.00 g HNO_3?
ans. 5.48g

2 )CO + 2H₂ --> CH₃OH
If the reaction has 35.4 g of CO and 10.2 g of H₂ how many grams of CH₃OH will be produced?
ans. 40.5

3) 2N₂O₅ --> 4NO₂ + O₂
If a sample of N₂O₅ produces 1.618 g of O₂, how many grams of NO₂ are formed?
ans.9.304g


_{This is a tutorial on dealing with Stoichiometry. Enjoy!}

-Catherine