Determining the Volume of a Product

(Partner: Victoria L.)

Procedure:

1) Put on safety goggles.
2) Put 3g NaHCO3 (baking soda) in the balloon.
3) Add 70ml HC2H8O2 (vinegar) to the Erlenmeyer flask.
4) Place the balloon over the top of the flask letting the baking soda drop into the flask.
5) When the reaction is complete, and the balloon stops inflating, take the string and tie off the balloon.

6) Place balloon in a beaker filled with 600ml of water until it is fully submerged. (new level: 1300ml water)

7) The actual volume of the balloon is calculated by subtracting first water level from the second water level.

Observations:

Analysis:

1)

2-4)














5) The balloon may not have been completely tied off, which would cause the volume to be lower. The first time we put the balloon in the water, the water level was too high and it overflowed out of the beaker.

6) We made the amount of water in the beaker lower and tied off the balloon tighter to secure all of the CO2 inside.

Calculating the Ideal Gas Constant

(Partner: Caitlin M.)


Observations:

Data:

Length of Mg strip = 2.7 cm
Mass of Mg = 0.19 g
T=Temperature of Water (same as temp of H2 gas) = 23 oC = add 273 to give 296 K
Ptotal=Atmospheric Pressure = 0.99 atm

V=Volume of gas = 36 mL = 0.036 L 

Calculations:

1)

2)

3)

4) 

5)

Post Lab Questions:


1) Why was it important for the stopper to have a hole in it? (What would happen if the stopper did not have a hole in it?)
- That way, we could make sure all of the air was out of the tube by putting the pipette through the hole and adding more water into the tube.


2) Why was it important to make sure that the eudiometer was filled completely with water before you inverted it? If it weren’t completely filled, how would this have affected the volume of H2 gas (too high or too low)? How would your value for R be affected? (Too high or too low?) Explain your reasoning.
- Because if it was not completely filled the volume of the gas in the tube would be a combination of H2 gas and air. It would make the volume of H2 too high and therefore the R too high.


3) How would the calculated number of moles of H2 gas (from calculation #2) be compared to your actual moles of H2 gas produced be affected if some of your magnesium did not react (Too high or too low)? How would your value for R be affected? (Too high or too low)? Explain your reasoning.
- If some of the magnesium didn't react, the moles of H2 gas would be too low because the H2 gas was formed from the chemical reaction of the magnesium and the liquid in the tube. To get the right amount of H2 gas, all of the magnesium would have to react. Since the volume of H2 was too low, the R would be too low as well.


4) When measuring the pressure of H2 gas in the tube. You rightly assumed that there was some water vapor in the tube along with the H2. Thus, you corrected our P value by subtracting out the pressure due to the water vapor. If you had not made this correction, would your pressure value be too high or too low? How would this have affected your R value? (Too high or too low)? Explain your reasoning.
- If we hadn't corrected the value of P, our pressure would have been too high because it would have included the pressure from the water vapor not just of the H2 gas. This also would have made the R value too high.


5) Was your value for R too high or too low? Give 2 reasons that could account for your specific results.
- Our R value was too low most likely because we lost some the contents in the tube as we transfered it over, which would lower the R value.

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.