Emission Spectroscopy

(Partner: Paul B.)


Observations: (Before):
Barium Chloride- white, small sand-like crystals
Calcium Chloride- white, small, shiny balls
Lithium Chloride- white, small, powdery crystals
Sodium Chloride- white, powdery, sugar-like crystals
Strontium Chloride- white, sugar-like crystals
Cupric Sulfate- blue-green sand-like crystals
Potassium Chloride- white, small sand-like crystals
Unknown 1- white, small sand-like crystals
Unknown 2- blue-green sand-like crystals

(During):

Sodium Chloride

  

Barium Chloride

Strontium Chloride

Lithium Chloride



Cupric Sulfate



Potassium Chloride



Unknown   #2



Unknown #1



Calcium Chloride (Left)
Lithium Chloride (Right)

Questions:

1) According to the modern theory of the atom, where may an atom's electrons be found?

          The electrons orbit the nucleus in electron clouds.

2) How do electrons become "excited"?

          When an electron gains an E, it jumps to a higher level.

3) How should the burner flame be adjusted?

          It can be adjusted by turning the piece at the top to the left or right.

4) Why should the wire loops used in the flame emission tests be returned to their appropriate salt container?

          If the loops are not place back in the appropriate container then it will cause the chemicals to mix, affecting the outcome of the experiment.

5) How can a contaminated loop be cleaned?

          To clean the loop, it should be ran under distilled water.

6) What is the identity of the unknown salt(s)?

          Unknown #1 is potassium chloride, and Unknown #2 is cupric sulfate (copper chloride)

7) Prior to its discovery of Earth, the existence of helium was first confirmed in the sun. Explain how this can be possible.

          When holding the spectroscope up to the light of the sun, it shows the helium spectrum of the sun.

Determination of the Mass Percent of Sulfate in an Unknown Sulfate Salt

(Partner: Nina T.)


Procedure:


Day 1:
1) Measure 25ml of BaCl₂ in a graduated cylinder.
2) Measure half a spoonful of sulfate salt in a beaker. Determine the mass of the salt and the beaker.
3) Pour 5ml BaCl₂ into the beaker. 
4) Use a stirring rod to stir the solution.
5) Continue to pour BaCl₂ until it stops reacting with the salt. 
6) Take filter paper and measure. Record.
7) Put filter paper into a funnel and place a ring stand over your beaker. 
8) Slowly pour solution from Beaker 1 into the funnel placed over Beaker 2. 
9) Rinse through filter with distilled H₂O, leaving BaSO4.
10) Take filter paper and place in oven. 


Day 2:
11) Take filter paper out of oven and record mass. By subtracting the weight of the filter paper from the new mass, you get the mass of the BaSO4. 
12) Use stoichiometry to determine the theoretical mass of the SO4.
13) Calculate the mass percent of sulfate.


Observations:


BaCl_{2:
          Before: Clear liquid, transparent, like water
Sulfate Salt: 
          Before: White solid, like salt
BaCl 2 + Sulfate Salt:
          Solution: Foggy white, thick liquid}

BaSO4:
          After heating: white, smooth, cracked, like chalk

Day 1 Data		Day 2 Data
Mass	Grams	Mass	Grams
Empty 100ml beaker	29.73g	Filter Paper with BaSO4	1.42g
Beaker with Sulfate Salt	31.95g	(BaSO4)	(0.94g)
(Sulfate Salt in beaker)	(2.22g)
Filter Paper	0.48g

0.94g BaSO4	1 mol	1 SO4	96.06g SO4
	233.39g BaSO4	1 BaSO4	1 mol

= 0.39g SO₄


Mass % =     mass SO4         x 100 
                  mass sulfate salt

Mass % =     0.39g SO4         x 100  = 17.6% = mass percent of SO₄

                   2.22g sulfate salt

% Error =      17.6 - 55.1       x 100 = 68% = percent error
                          55.1

The Determination of the Mass of a Product of a Chemical Reaction

(Partner: Nina T.)


Observations:

 Day 1: NaCHO3 (Baking Soda) + HCl
                                                 
                                         Before: - very white powder with some clumps
                                           
                                         During: - the NaCHO3 bubbled quickly, then popped with smoke
                                                       - less and less NaCHO3, no chunks       
                                                       - solution becomes milk-like in color
                                                       - NaCHO3 not dissolved in HCl     
                                                       - with each drop of HCl, more and more bubbles appear 
                                                       - solution becomes clearer and less NaCHO3 is visible

Day 2: NaCHO3 (Baking Soda) + HCl --> NaCl + CO2 + H2O

                                                 

                                         Before: - NaCl formed up along sides of beaker

                                                       - yellow at top edges

                                                       - large NaCl bubbles at bottom of beaker
               

                                           

                           

                                            

                                         

                                         During: - the NaCl begins to make a slight pop noise

                                                       - yellow edges at top become light tan

Day 1 Data		Day 2 Data
Mass	Grams	Mass	Grams
Empty 150ml beaker	73.39g	NaCl plus beaker (first weighing)	78.89g
NaHCO3 in beaker	81.19g	NaCl plus beaker (second weighing)	78.85g
		NaCl plus beaker (third weighing)	78.79g

Discussion Questions:


1) Write the grams of NaHCO₃ you had in your beaker.
          81.19g - 73.39g = 7.8g NaHCO₃


2) Calculate how many moles of NaHCO₃ the mass is.
                                                                                     

7.8g NaHCO3	1 mole
	84.02g NaHCO3

= 0.09 mol NaHCO₃ 

3) Write the molar ratio for the NaHCO₃ / NaCl ratio. 

         1 NaHCO₃ : 1 NaCl

4) Write the number of moles of NaCl you predict were produced in your experiment. 

7.8g NaHCO3	1 mol	1 NaCl
	84.02g NaHCO3	1 NaHCO3

= 0.09 mol NaCl 


5) Calculate the mass of NaCl you predict will be produced.

7.8g NaHCO3	1 mol	1 NaCl	58.45g NaCl
	84.02g NaHCO3	1 NaHCO3	1 mol

= 5.43g NaCl

6) Determine, by subtraction, the actual mass of NaCl produced in your experiment. 

   a) First weighing:  78.98g NaCl - 73.39g (mass of beaker) = 5.59g NaCl

   b) Second weighing:  78.85g NaCl - 73.39g = 5.46g NaCl

   c) Third weighing:  78.79g NaCl - 73.39g = 5.40g NaCl

7) Calculate your percentage yield. 

5.4g NaCl

5.43g NaCl x100 = 99% yield

8) What are plausible reasons why your percent yield is less than 100%?

         -We did not use enough NaHCO_3.

9) What are plausible reasons why your percent yield is more than 100%?

         -We used too much NaHCO_3.