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Bellwork:
1. write and balance this equation: Aluminum and hydrochloric acid
(HCl) react to form aluminum chloride and hydrogen gas
2. What is the mass of 0.50 moles of aluminum?
3. If 2 moles of aluminum reacts, how many moles of hydrochloric acid is
required?
4. If 4 moles of aluminum reacts, how many moles of hydrochloric acid is
required?
5. If 1 moles of aluminum reacts, how many moles of hydrogen gas is
formed? What is the mass? How many molecules is that? If one mole of
a gas is 22.4L, how many L is that?
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Stoich_notes_smartboard_s2017_4th.notebook
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Stoichiometry Lab
Aluminum metal reacts with hydrochloric acid to form hydrogen gas and an aluminum chloride solution. In this investigation, you will predict the mass of hydrogen gas produced by a given amount of reactants, then measure the amount, and compare them.
Hydrochloric acid is an aqueous solution of hydrogen chloride. The concentration is usually described in terms of “moles per liter” which is abbreviated “mol/L” or “molar” or “M.” The most concentrated hydrochloric acid is 12 M, but for safety reasons we will be using a solution that is 3.0 M.
Safety...
Procedure
1. Put on a pair of safety goggles, and open your lab notebook to a new page.
2. Obtain approximately 0.25 grams of aluminum foil. Record the exact mass, and tear it into tiny pieces.
3. Put 50.0 mL of the hydrochloric acid into a small beaker. Record the mass of the beaker with solution in it.
4. Place the foil pieces on the balance tray next to the beaker of acid, and record the total mass. [If this total mass does not equal the sum of number 2 and 3, you should remeasure.]
5. With the beaker still on the balance, drop the foil into the acid and observe. What happens to the overall mass?
6. When the aluminum is gone, record the final mass of the beaker with the solution.
7. Dispose of the materials in the beaker according to your teacher’s instructions.
Data Table
1. mass of Al __________g
2. mass of flask/acid ________g
3. mass of flask/acid/Al
BEFORE reaction _________g
(this should be the same as 1+2)
4. mass of flask/acid/Al
AFTER reaction __________g
5. mass of H2(g) released ________g
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STOICHIOMETRY: tells relative amounts of reactants & products in a chemical reaction • Given an amount of a substance involved in a chemical reaction, we can figure out the amount of the other substances are needed or produced • Always compare the number of MOLES • 4 Fe + 3 O2 ­­> 2 Fe2O3 • If I have 4 moles of Fe, I need 3 moles of O2 in order to produce 2 moles of Fe2O3. • Comparison of coefficients = MOLE RATIO • In the above equation, what is the mole ratio between Fe2O3 and O2? • Use coefficients… 2 moles Fe2O3 : 3 moles O2 or 2 moles Fe2O3 to 3 moles O2
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p. 357 # 2c and 3a
­write all possible mole ratios
2c. 4Zn + 10HNO3 ­­> Zn(NO3)2 + N2O + 5H2O
3a. 4Al + 3O2 ­­> 2Al2O3
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p. 356 # 1
Interpret the following balanced chemical equations in terms of particles, moles and mass. Show that the conservation of mass is observed.
a. N2(g) + 3H2(g) ­­> 2NH3(g)
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SOLVING STOICHIOMETRY PROBLEMS… ** WRITE THE BALANCED EQUATION & GIVEN INFORMATION! **
1.) Find moles of given element or compound. 2.) Use mole ratio (coefficients) from balanced equation.
­put box around mole ratio in each problem! 3.) Find answer. ­be sure to write the formula of each substance throughout the problem and in your answer!
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Example 1: If 34.32 grams of acetylene (C2H2) are burned in air, how many moles of CO2 can be formed? What do we have?
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Example 2: What mass of Na2CO3 are needed to react completely with 6.21 moles of Ca(OH)2? 8
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• What is the limiting reactant when 28g of N2 reacts with 25g H2? How much NH3 will be formed? 15
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