1. Mass and gaseous volume relationships in chemical reactions
Topic 1 – Quantitative Chemistry

2. Reacting masses
Stoichiometry
Combustion of methane

3. Mass Conversions (the world of stoichiometry)
__Al (s) + __I2 (s)  __AlI3 (s)
35.0 g of Al will react with how many grams of I so there is no excess reactant?
Step 1  convert known into moles
Step 2  convert moles of known into moles of unknown
Step 3  convert moles of unknown into grams of unknown

4. Example
10.00 grams of sodium hydroxide is reacted with excess sulfuric acid in the following reaction:
2NaOH(s) + H2SO4(aq)  Na2SO4(aq) + H2O(l)
What mass of Na2SO4 · 7H2O is produced?

5. example
Sodium hydrogen carbonate decomposes into sodium carbonate, water, and carbon dioxide when heated. How much Sodium hydrogen carbonate is needed to produce 8.80 g of CO2?

6. example
How much oxygen gas is required for the complete combustion of .250 mol. of propane gas (C3H8)?

7. example
Solid lithium hydroxide is used to remove carbon dioxide from the environment. The products are solid lithium carbonate and liquid water. What mass of carbon dioxide can 1.00 x 103 g of lithium hydroxide absorb? How much water is produced?

8. Example 3
Baking soda (NaHCO3) and Milk of magnesia are antacids to neutralize excess HCl in the stomach
Balanced equations:
NaHCO3(s) + HCl(aq)  NaCl(aq) + H2O(l) + CO2(g)
Mg(OH)2(s) + 2HCl (aq)  2H2O(l) + MgCl2(s)
Which antacid is better?

9. Limiting reactants
Methane reacts with water to produce hydrogen gas and carbon monoxide
What quantity of water is required to react exactly with 249g of methane?
What if you have 300.g of water

10. Limiting Reactant
What if there are not exact combinations of reactants?
One reactant will run out before the other is used up
One reactant is in excess
The limiting factor is what determines the amount of product that can be formed

11. Example
Ammonia is an important fertilizer to farmers and is produced by combining nitrogen gas and hydrogen gas. If you have 25.0 kg of nitrogen gas is reacted with 5.00 kg of hydrogen gas. How much ammonia is going to be produced?

12. Steps to solve Step 1 – when in doubt convert to moles
Step 2 – Determine the limiting reactant
Step 3 – calculate the mass of product using the limiting reactant

13. Example
Nitrogen gas can be created by passing gaseous ammonia over solid copper (II) oxide at high temps. Other products formed are solid copper and water vapor.
If you have 18.1g of NH3 and 90.4 g of CuO. How many grams of Nitrogen can be produced?

14. Do we get all that product?
Why?
Percent yield = actual yield / theoretical yield
If in the last problem you actually obtained g of nitrogen what was the percent yield of the reaction?

15. Example
68.5 kg of CO(g) is reacted with 8.60 kg of H2(g) to form methanol (CH3OH). What is the theoretical yield? If you actually produce 3.57x104 g what is the percent yield?

16. Example
Lithium nitride is prepared by the reaction of lithium metal and nitrogen gas. Calculate the amount of lithium nitride formed when 56.0 g of lithium react with 56.0 g of nitrogen.

17. Example
Titanium (IV) oxide is a solid white used as a coloring pigment is made by reacting gaseous titanium (IV) chloride with oxygen gas. Chlorine gas is also formed as a by-product. If 6.71x103 g of titanium (IV) chloride is reacted with 2.45x103 g of oxygen, how much titanium (IV) oxide can be produced? If the percent yield is 75.0%, how much titanium (IV) oxide was actually produced?

18. Avogadro’s laws in gasses
Avogadro’s hypothesis – at a standard temperature and pressure all gasses will occupy dm3 mol-1. (STP = 1 atm & 273K)
2CO2(g) + O2(g)  2CO2(g)

19. Calculations
10 cm3 of ethyne is reacted with 50 cm3 of hydrogen to produce ethane in the following equation:
C2H2(g) + H2(g) C2H6(g)
Calculate the volume of the ethane gas, and any remaining reactant.

20. Molar volume of a gas Mol of a gas = Volume of gas / molar volume
Calculate the number of moles and mass of oxygen gas in 5.00 dm3 of oxygen at STP.

21. example
What mass of sodium hydrogen carbonate must be heated to create dm3 of carbon dioxide at STP?

22. What volume of air (20% oxygen) is needed to completely combust 1
What volume of air (20% oxygen) is needed to completely combust kg of gasoline (C3H8) at STP?

23. Ideal gas

24. Boyle’s law Volume pressure P x V 48.0 29.1 40.0 35.3 32.0 44.2 24.0
58.2

25. Examples
What is the new volume of 1.5 L sample of Freon –12 at 56 torr compressed to 150 torr?
In an automobile the initial volume of an engine cylinder is .725 L and an initial pressure of 1 atm. If the piston is moved to a volume of .075 L what will the new pressure be?

26. Charles’s Law

27. Example
A 2.0 L sample of air is collected at 298 K and cooled to 278 K, what is the new volume?
A gas has an original volume of .675L and a temp. of 35.0 oC. If the volume is changed to L what is the temperature of the gas?

28. Lussac’s Law

29. Combined gas law
A syringe contains 50 cm3 of gas at 1.0 atm and 20.0oC is heated to 100.0oc and changed to 5.0 atm.
What is the new volume?

30. Ideal Gas Law
All of the gas law constants can be combined to help create a general equation
What are all the laws thus far?
R is the gas constant
R = when P is atm and V is L
Use the ideal gas law when gas is at 1 condition
Works best when gas is at low pressure (1atm or less) and higher temp (above 0oC)
Equation PV=nRT

31. Example
A sample of hydrogen gas has a volume of 8.56 L at 0oC and a pressure of 1.5 atm. How many moles of hydrogen are there? Molecules of Hydrogen?

32. Example II
What volume is occupied by .250 mol of carbon dioxide at 25oC and .488 atm?

33. Example III
.240 mol sample of ammonia at 25oC with a volume of 3.5 L and a pressure of 1.68 atm. The gas is compressed to a volume of 1.35 L What is the final pressure