Ms. Bowser
Chemistry
3/6/2016
Can I have change for that?
Purpose: To look and study examples of physical and chemical changes and how these changes relate to the mass of the reactants and products.
Hypothesis:
- Equation: NaCl (s) ->NaCl (aq)
Hypothesis: The mass will be the same before and after combining (because of conservation of mass) the H2O and NaCl (s) to form NaCl (aq)
2. Equation: Na2CO3 (aq) + CaCl2 (aq) -> 2NaCl(aq) + CaCO3 (s)
Hypothesis: The mass of the products and reactants in this experiment will be the same (due to the law of conservation of mass)
3. Equation: Na2CO3 (aq) + 2C2H4O (aq) -> 2NaC2H3O2 (aq) + H2O (l) + CO2 (g)
Hypothesis: The mass in this experiment will decrease after the reactants are combined; because a gas will form (CO2 (g)) which will escape the beaker therefore decreasing the total mass of the combined products.
Procedure:
For each of the three equations, weigh the mass of the reactants before and after combining. Measure reactants as instructed for each of the equations. Be sure to measure both masses with both containers on the scale.
(Martyn F. Chillmaid)
Equation 1: 1 gram of NaCl (s) and 20 mL of water (H2O) in separate containers.
Equation 2: 20 mL of Na2CO3 (aq) and 20 mL CaCl2 (aq) in separate containers.
Equation 3: 20 mL of Na2CO3 (aq) and 20 mL of C2H4O2 (aq) in separate containers.
Safety:
NaCl irratent to eye, skin and if ingested or inhaled (Material Safety Data Sheet: Sodium Chloride MSDS)
H2O, Non-corrosive, non-irratant, non permeator for skin. (Material Safety Data Sheet. Water MSDS.)
Na2CO3 (aq), irratint to eyes and skin. Can cause lung irritation and blindness. severity of skin corrosion depends upon length of time substance on skin. ( Material Safety Data Sheet: Sodium carbonate monohydrate MSDS)
CaCl2 (aq), irratant to skin, eyes, and if ingested or inhaled. Can permeate skin and harmful ( Material Safety Data Sheet: Calcium chloride anhydrous MSDS).
C2H4O2 (aq), irratint to skin, eyes and if ingested or inhaled. Permeates skin (Material Safety Data Sheet: Methyl Formate MSDS)
Materials:
- Balance
- Transparent plastic cups
- water
- NaCl (s), 1 g
- 1.0 M Na2CO3 (aq) 40 mL
- 1.0 M CaCl2 (aq)
- Acetic Acid, C2H4O2, 20 mL
- Graduated Cylinder
Background
The Law of Conservation of Mass states that matter can be changed from one form to another without the mass of the matter fluctuating. At the micro level, this means that no single atoms are gained or lost (excluding error) during the experiment. For the macro level, we can weigh the amount of mass in matter before and after the experiment to prove this law (The Law of Conservation of Mass.)
Data:
Reaction #1
Reactants/Products: Chemical Name Description Mass before Mass after
____________________________________________________________________________
NaCl(S) Sodium Chloride Light colored powder 23.45
H2O Water Clear liquid
____________________________________________________________________________
NaCl (aq) Sodium Chloride (aq) Cloudy in the water 23.425
____________________________________________________________________________
Reaction #2
Reactants/Products: Chemical Name Description Mass before Mass after
_________________________________________________________________________________
Na2CO3(aq) Sodium Carbonate (aq) Watery substance 45.70
CaCl2 (aq) Calcium Chloride Watery and pale _________________________________________________________________________________
CaCO3 (s) Calcium Carbonate Powder in cloudy water 45.673
NaCl (aq) Sodium Carbonate Watery
Reaction #3
Reactants/Products: Chemical Name Description Mass before Mass after
_________________________________________________________________________________
Na2CO3 (aq) Sodium Carbonate Thin/ watery 41.7
C2H4O2 (ag) Vinegar Clear, liquid
_________________________________________________________________________________
NaC2H3O2 (aq) Sodium Carbonate Clear liquid 40.1
CO2 (g) Carbon dioxide Clear gas
_________________________________________________________________________________
Calculations:
In reaction #3) 41.7- 40.1= 1.6
1.6 mL of gas escaped during the 3rd experiment.
Percent Error
Reaction # 1 = .09 %
Reaction #2 = .044%
Reaction #3 = 3.84%
Discussion of Error
The error in this lab was due to the swishing method in which the products were combined using a method of swishing the tubes to insure proper combination of the compounds. This method perhaps led to stray drops falling from the test tube; thus, a decrease in the compounds overall mass. In experiment #3, the reason for such a large percent error was really not an error; rather, the gas that was formed in the container during the reaction escaped the container thus decreasing the overall final mass.
Questions:
5) SO3 (g) + H2O (l) -> H2SO4 (aq)
H2SO4 could be ingested or absorbed through the skin.
6) 2Li + 2HCl -> H2 + 2LiCL (aq) + H2 (g)
2LiCl could be absorbed through the skin or be ingested. H2 could be inhaled.
7) AgNO3 (aq) + NaOH (aq) -> NaNO3 (aq) + AgOH (aq)
Could be ingested or absorbed through the skin.
Conclusion:
The hypothesis of this lab was correct in all the predictions of the masses of the three reactions before and after the experiment. The purpose of this lab was fulfilled in that the class studied physical and chemical changes and related these changes to mass.
Citations:
Martyn F. Chillmaid. Science Photo Library. http://www.sciencephoto.com/media/4621/view
Sciencelab.com. Chemicals and laboratory equipment. (5/21/2013). Material Safety Data Sheet: Sodium Chloride MSDS. Retrieved from: http://www.sciencelab.com/msds.php?msdsId=9927593
Sciencelab.com. Chemicals and laboratory equipment. (5/21/2013). Material Safety Data Sheet: Water MSDS. Retrieved from http://www.sciencelab.com/msds.php?msdsId=9927321
Sciencelab.com. Chemicals and laboratory equipment. (5/21/2013). Material Safety Data Sheet: Sodium carbonate monohydrate MSDS. Retrieved from: http://www.sciencelab.com/msds.php?msdsId=9927591
Sciencelab.com. Chemicals and laboratory equipment. (5/21/2013). Material Safety Data Sheet: Calcium chloride anhydrous MSDS. http://www.sciencelab.com/msds.php?msdsId=9923251
Sciencelab.com. Chemicals and laboratory equipment. (5/21/2013). Material Safety Data Sheet: Methyl Formate MSDS. http://www.sciencelab.com/msds.php?msdsId=9926061
The Law of Conservation of Mass. http://www.chem.wisc.edu/deptfiles/genchem/sstutorial/Text1/Tx14/tx14.html
