Download Conservation of Mass Lab

Title: Conservation of Mass
Introduction/Purpose: To prove conservation of mass law. Look up conservation of
mass law. Provide answer.
State hypothesis.
Pre Lab: Look up background information on Antoine Lavoisier and disclose a small
biography and his significant contributions to chemistry.
Materials: Erlenmeyer flask, antacid tablet/ balloon, water, scale.
Procedure:
1. mass tablet
_________grams
2. mass erlenmeyer with about 3/4 full of water
3. mass ballon
________grams
_________grams
4. Total mass of steps 1,2,3.
________grams
5. have one lab partner hold erlenmeyer flask firm with one hand, drop the antacid tablet
into flask and water then quickly have a lab partner secure a ballon on top of the
erlenmeyer flask not letting any gas escape.
6. After tablet has dissolved mass the apparatus (balloon, flask water and gas released)
_________grams
Observations: Please list observations. Draw diagram neatly of experiment.
Data:
Mass of all materials before experiment. Line 4:
________grams
Mass of all materials after experiment. Line 6
_________grams
Perform percent error calculations (formula in chemistry reference tables):
write formula and show all work. Box answer.
Discussion/ Analysis
1. Discuss how this experiment proves or disproves the law of conservation of mass.
3. A student performs the above experiment. His original mass before the experiment
was 215.5 grams and after the experiment it was 212.4 grams. What was his
experimental error? Show calculations.
4. Why do you think some mass was lost?
Conclusion: Worksheet. Show Calculations
Fill in the blank with the correct number, and write a balanced equation with the the
correct formulas.
1. 40 g of calcium reacts with 71 g of chlorine to produce _____ g of calcium chloride.
2. _____ g of potassium reacts with 16 g of oxygen to produce 94 g of potassium oxide.
3. 14 g of lithium reaction with _____ g sulfur to produce 46 g of lithium sulfide.
4. 24 g of magnesium reacts with 38 g of fluorine to produce _____ g magnesium
fluoride.
5. 65.5 g copper reacts with _____ g oxygen to produce 81 g copper (I) oxide.
6. 88 g of strontium reacts with 160 g bromine to produce _____ g strontium bromide.
7. 46 g of sodium reacts with _____ g chlorine to produce 117 g sodium chloride.
8. ____ g iron reacts with 71 g chlorine to produce 129 g of iron (II) chloride.
9. 137 g of barium reacts with ______ g iodine to produce 391 g barium iodide.
10. _____ g hydrogen reacts with 32 g of oxygen to produce 34 g of hydrogen
peroxide.
Balancing Chemical Equations
You may remember that the law of conservation of mass says that matter is neither created nor destroyed
during a chemical reaction. This means that all chemical reactions must be balanced—the number of
atoms, moles, and ultimately the total mass must be conserved during a chemical process. Here are the
rules to follow when balancing equations:
1.
Determine the correct formulas for all the reactants and products in the reaction.
2.
Begin balancing with the most complicated-looking group. A polyatomic ion that appears
unchanged on both sides of the equation can be counted as a single unit.
3.
Save the elemental (single elements) reactant and products for last, especially if it is hydrogen or
oxygen. Keep your eye out for diatomic molecules such as oxygen, hydrogen, and the halogens.
4.
If you get stuck, double the most complicated-looking group and try again.
5.
Finally, make sure that all coefficients are in the lowest-possible ratio.
6.
Know when to quit! None of the reactions you will encounter will be that difficult. If the
coefficients are getting wild, double-check what you’ve done since you may have a simple mistake.
When balancing reactions, keep your hands off the subscripts! Use only coefficients to balance chemical
equations. Now let’s try an example. When you solve it yourself, make sure to follow the steps!
Example
Write the balanced equation for the reaction between chlorine and sodium bromide, which produces
bromine and sodium chloride.
Explanation
First write the chemical formulas—be on the lookout for the diatomic elements (such as Cl 2):
Cl2 + NaBr
Br2 + NaCl
Next, find the reagent with the scariest subscripts. In this case, start with Cl2. You need a coefficient of 2 in
front of NaCl, which then requires a coefficient of 2 in front of NaBr. The balanced equation becomes
Cl2 + 2NaBr
Br2 + 2NaCl
Finally, count up everything to make sure you balanced the equation correctly. You have two chlorine
atoms, two sodium atoms, and two bromines on the reactants side and two bromines, two sodiums, and
two chlorines on the products side. You’re done.
Example
Write the balanced equation for the reaction between aluminum sulfate and calcium chloride, which
produces aluminum chloride and calcium sulfate.
Explanation
Write the chemical formulas on their correct sides:
Al2(SO4)3 + CaCl2
AlCl3 + CaSO4
In this reaction, the aluminum sulfate looks the most complicated, so start there. Look at what happens
with sulfate—since it remains sulfate on the right side of the reaction, treat it as a unit. You have three on
the left side and only one on the right side, so place a coefficient of 3 in front of calcium sulfate. Now deal
with the aluminum. You have three on the left and one on the right, so place a coefficient of 2 in front of
aluminum chloride. Last, you must place a coefficient of 3 in front of calcium chloride.
Al2(SO4)3 + 3CaCl2
2AlCl3 + 3CaSO4
Count the atoms on both sides of the reaction and you’ll see that you’re done.