1. Welcome Back!! New Year’s Resolution—sit in your seat as you read the board. Make sure you start going to the blog on a nightly basis. I am thinking about getting rid of journals if you start going to the blog. ?? or  ?? Read the information about Honors Chem and post a comment to me tonight. Today we will be reviewing stoichiometry. Tomorrow we will be taking our stoichiometry quest—not a partner quest.

2. Stoichiometry Review Silver sulfide (Ag 2 S) is the common tarnish on silver objects. What weight of silver sulfide can be made from 1.23 mg of hydrogen sulfide (H 2 S) obtained from a rotten egg? The reaction of formation of silver sulfide is given below: 4Ag + 2H 2 S + O 2  2Ag 2 S + 2H 2 O 0.00897 g silver sulfide

3. Stoichiometry Review A somewhat antiquated method for preparing chlorine gas involves heating hydrochloric acid with pyrolusite (manganese dioxide), a common manganese ore. (Reaction given below.) How many kg of HCl react with 5.69 kg of manganese dioxide? 4HCl + MnO2  2H2O + MnCl2 + Cl2 9.56 kg HCl

4. Stoichiometry Review A typical automobile gets 30 miles per gallon of gas and drives 12,000 miles every year. Assuming that octane (C 8 H 18, density 0.7025 g/mL—3.78L = gal) is a principal component of gasoline; How much oxygen is required for a car to run for 1 year? (Start with 12,000 miles and step by step go to grams octane—then normal stoich) How much CO 2 is produced by the car in 1 year? How many trees are required to remove the CO 2 produced by the car in 1 year? (Avg tree removes 50 lb CO2 per year—2.2lb = 1 kg)

5. Stoichiometry Review The Kingston Steam Plant burns 14,000 tons of coal each day and generates 1010 kilowatt - hours of electricity each year (enough for 700,000 homes). Coal is primarily carbon which undergoes combustion in the following reaction: C (s) + O 2 (g)  CO 2 (g) How many grams of oxygen is required for the combustion of 1 day's coal? (2000 lb = 1 ton, 2.2lb = 1kg) How much carbon dioxide is produced each day? How many trees are required to remove the CO 2 produced by the KSP in 1 year? (Avg tree removes 50 lb CO2 per year—2.2lb = 1 kg)

6. Stoichiometry Review CO2 is removed from the atmosphere by trees & converted into cellulose. The basic reaction for this is: 6 CO2 + 5 H2O  C 6 H 10 O 5 + 6 O2 How many grams of water are required to process the CO2 from one day's electrical production at the Kingston Steam Plant? How much oxygen is produced by this process? How much cellulose is produced?

7. Stoichiometry Review An organic chemist reacted 10g CH 4 with excess Cl 2 and obtained 10g of CH 3 Cl. (Hydrogen gas is also produced.) What should have been the theoretical yield. What was their percentage yield?

8. AP Review 1. 5.12 g of Mg(NO 3 ) 2 is dissolved in 800.2g of water. The kb for water is 0.512°C/m. Assume complete dissociation of the salt. What is the boiling point elevation in K? 2. What is the vapor pressure of an ideal solution containing 61.1g of, CHCl 3, and 70.9g of carbon tetrachloride, CCl 4 at 25°C? The vapor pressures at 25 °C are 172.0 torr for pure CHCl 3 and 98.3 torr for pure CCl 4.

9. AP Review AP Review 3. How many grams of ethanol, CH 3 CH 2 OH, are needed to raise the boiling point of 500mL of water by 2.5°C? The boiling point elevation constant kb = 0.512 °C/molality. 4. What is the molecular weight of a covalent compound containing 101g/L if it has an osmotic pressure of 0.711 torr at 25°C? 5. Assuming the van’t Hoff factor for NaCl to be 2, calculate the freezing point of an aqueous 0.500 molal NaCl solution? For water, Kf = 1.86oC/m.

10. AP Review 6. A non-volatile liquid with formula C 2 H 6 O 2 and molar mass 62g/mol, is added to 2102g of water. At 89 o C, the vapor pressure of this resulting solution is found to be 460 torr. How many grams of the non- volatile liquid were added to the water? (The vapor pressure of pure water is 526 torr at 89 o C). 7. Find the boiling point of a solution containing 14.59g NaCl in 84.0g water? Kb for water is 0.512 o C/m.