ENERGY EXAM REVIEW WORKSHEET #2 More Math Practice  1. How many kilojoules of heat energy are required to heat all the aluminum (c=0.902J/g.K) in a roll of aluminum foil (500. g) from room temperature (25.0 oC) to the temperature of a hot oven (250.0 oC)? 2. I found this question online. It’s pretty ridiculous. Bonus points if you can find the flaw in the problem and justify it mathematically…: One way to cool down your cup of coffee is to plunge an ice-‐cold piece of aluminum into it. (Believe it or not, this isn’t the ridiculous part yet!) Suppose you store a 20.0 g piece of aluminum in the refrigerator at 4.40 oC and then drop it into your coffee. The coffee temperature drops from 90.0 oC to 55.0 oC. How many joules of heat energy did the aluminum block absorb? Ignore the cooling of the cup. 3. An 18.7 g sample of platinum metal increases in temperature by 2.30 oC when 5.70 J of heat are added. What is the specific heat of platinum. Give units. 4. Standard enthalpies of formation are: C2H5OH(l) Δ Hf = -‐228, CO2 Δ Hf = -‐394, and H2O(l) Δ Hf = -‐ 286 kJ/mol. Calculate the enthalpy of the reaction, C2H5OH + 3 O2  2 CO2 + 3 H2O CONCEPTS…. 5a. In a heating curve for water, why is the line segment for boiling/evaporation so much longer than the line segment for melting? (Use the term “intermolecular forces” in your answer.) 5b. Use a heating curve in your answer: Can ice be less than zero degrees Celsius? 6. Identify each process as exothermic or endothermic: vaporization, freezing, sublimation, melting, combustion, condensation, deposition, boiling MOoore Maaathththththhhh 7. How much heat will be released when 6.44 g of sulfur reacts with excess O2 according to the following equation? 2S + 3O2  2SO3 Δ H = -‐791.4kJ 8. How much heat will be absorbed when 5.81 g of carbon reacts with excess H2 according to the following equation? 6C + 3H2  C6H6 ΔH = 49.03kJ 9. Calculate the heat of vaporization of water at its boiling point when 23.0 g of water requires 51.98 kJ to vaporize. Give units. ENERGY EXAM REVIEW WORKSHEET #2 I Know You Want a Few More Math Problems… 10. The combination of coke and steam produces a mixture called coal gas, which can be used as a fuel or as a starting material for other reactions. If we assume coke can be represented by graphite, the equation for the production of coal gas is 2 C (s) + 2 H2O (g) → CH4 (g) + CO2(g) Determine the standard enthalpy change for this reaction from the following standard enthalpies of reaction : (1) C(s) + H2O (g) → CO (g) + H2 (g) ΔH° = 131.3 kJ (2) CO (g) + H2O (g) → CO2 (g) + H2 (g) ΔH° = - 41.2 kJ (3) CH4 (g) + H2O (g) → 3 H2 (g) + CO (g) ΔH° = 206.1 kJ The next one is challenging!!! 11. One reaction involved in the conversion of iron ore to the metal is FeO (s) + CO (g) → Fe (s) + CO2 (g) Calculate the standard enthalpy change for this reaction from these reactions of iron oxides with CO : (1) 3 Fe2O3 (s) + CO (g) → 2 Fe3O4 (s) + CO2 (g) ΔH° = - 47.0 kJ (2) Fe2O3 (s) + 3 CO (g) → 2 Fe (s) + 3 CO2 (g) (3) Fe3O4 (s) + CO (g) → 3 FeO (s) + CO2 (g) ΔH° = - 25.0 kJ ΔH° = 19.0 kJ MORE MATH CHALLENGES! (There are some values that you will need to look up.) 12. A 5.0 kg chunk of gold (specific heat 0.129 J/g.K) is cooled to -‐272oC and then is tossed into a container holding 0.100 kg of steam at 110oC. The container is sealed and insulated. After thermal equilibrium is achieved, what will be the temperature of the chunk of gold? (Does it get any CRAZIER than this???) 13. 40.0 grams of aluminium at 20 degrees Celsius and 3.0 grams of iron at 90.0 degrees Celsius are both tossed into 100.0 mL of water at 70.0 degrees Celsius. What is the final temperature of the mixture when it reaches thermal equilibrium? (THIS must be IMPOSSIBLE, WHO would ATTEMPT a problem like THIS?!) Concept? Or is it math? You decide…. 14. A gas absorbs 2.5 J of heat and has 3.1 J of work done on it. What is the change in internal energy? 15. A gas absorbs 4.1 J of heat and performs 6.2 J of work. What is the change in internal energy? 16. Calculate the work (in L.atm) with the expansion of a gas from 25 liters to 37 liters at a constant pressure of 1.5 atm. 17. Calculate the work (in L.atm) with the compression of a gas from 92 liters to 88 liters at a constant pressure of 2.2 atm.