1. CHEMISTRY SEMESTER REVIEW LAST CALL FOR QUESTIONS

2. Do you remember how to identify the type of reaction? 2 H 2 O → 2 H 2 + O 2 –What type of reaction is this? Decomposition Reaction C 10 H 8 + 12 O 2 → 10 CO 2 + 4 H 2 O –What type of reaction is this? Combustion Reaction

3. GRAMS to MOLECULES How many molecules are there in 250g of NH 3 ? What do we do first? First thing to do is find the molar mass of the compound. Molar mass is the sum total of every atom’s mass in the compound.

4. What's the molar mass of NH 3 ? NITROGEN(N) = 14.01g/mol HYDROGEN(H) = 1.008g/mol

5. What's the molar mass of NH 3 ? N = 14.01 g H = 1.008 g (times 3 because there are three hydrogen atoms in NH3) The molar mass is 17.034 g/mole (or 17.034 grams per 1 mole of NH3)

6. Next Step (250g of NH 3 ) Next, once you know the total mass of your substance, you can convert to moles by dividing the total mass of NH3 (250 g) by the molar mass (17.034 g/mol). 250 g1 mol (of NH 3 ) 17.034 g 14.68 mol =

7. Finally, the number of molecules can be calculated To do this you must convert moles to molecules using Avogadro’s #, which is 6.02 X 10 23 14.68 mol 6.02 x 10 23 molecules 1 mol 8.837 x 10 24 = molecules

8. TYPES OF SYSTEMS

9. open systems can exchange mass and energy closed systems allow the transfer of energy (heat) but not mass isolated systems do not allow transfer of either mass or energy

10. HYDROGEN EXPLOSIONHYDROGEN EXPLOSION - combustion Is this reaction taking place in an open, closed or isolated system? the reacting mixture is the system (hydrogen, oxygen, and water molecules)......everything else is the surroundings This is exothermic because it is a combustion reaction (thermal energy leaves during this and all other exothermic reaction -- a lot of thermal energy is released in this example... ） open system

11. What's an example of an isolated system?

12. Calorimetry - "the measurement of heat change" a "calorimeter" is an insulated, closed container that creates an ISOLATED SYSTEM a specific quantity of water surrounds a system carrying out a reaction during the reaction, heat leaves the inner container and is absorbed by the surrounding water by recording temperature change, the heat generated by a reaction can be calculated

13. Heat Capacity –heat needed to raise a certain quanity of a substance 1 degree (celsius) Specific Heat –the heat needed to raise a 1 gram of a specific substance 1 degree (celsius)

14. If volume and pressure remain constant, then q = H Either heat capacity or specific heat must be applied to find a substances change in heat. Remember... heat capacity specific heat Δt x (C) = m x (s) x Δt °C

15. Practice Question A quantity of 1.435 g naphthalene (C 10 H 8 ) is burned in a calorimeter. The water temp. rises from 20.28 to 25.95 degrees celsius. If the heat capacity (C) is 10.17 kJ/celsius, calculate the molar heat combustion of C 10 H 8. What is being asked here: How much heat per mole of napthalene is released into the calorimeter? To do this: You need to figure out how much heat is generated by the combustion You need to convert this total heat to q per mole (kJ/mol)

16. solving this problem...

17. We are not done... The question asks us to calculate "the molar heat of combustion." So, you have to find the molar mass of naphthalene (C 10 H 8 ) have to use periodic table... molar mass of C 10 H 8 is 128.2 g now we can convert from kJ/1.435 g to kJ/mol

18. How to convert...

19. INTENSIVE and EXTENSIVE PROPERTIES Extensive Properties - are properties that depend on how much matter is being considered –for example: volume the property of space a substance takes up is a value dependent on how much of the substance there is. –Can you think of others...

20. INTENSIVE and EXTENSIVE PROPERTIES Intensive Properties - properties that do NOT depend on how much matter is being considered –for example: boiling point the boiling point of liquid water into water vapor is the same regardless of how much water there is. –can you think of others...

21. MOLE vs. MOLARITY mole (mol) 1 mol = 6.02 x 10^23 particles of a particular substance molarity (M) molarity or molar concentration is the number of moles of solute per liter of solution the dissolved substance A solvent is what a solute dissolves in to make a solution

22. molarity is defined as... molarity = moles of solute / liters of solution So, is molarity an intensive or extensive property? intensive property

23. Change in Enthalpy of a Reaction

24. Standard Enthalpy of Formation DEFINITION: –the enthalpy of a reaction carried out at 1 atm and at 25 degrees C –the enthalpy value relates to the heat absorbed or released during the formation of 1 mole of a specific compound The symbol for this value is represented as: Once we know these values, we can calculate the change in enthalpy of a reaction, or...

25. Standard Enthalpy of a Reaction n = the coefficient of the products m = the coefficient of the reactants Σ = "the sum of" f = formation ° = standard state conditions (1 atm and 25 degrees C) m

26. The most stable forms of substances will = 0 Given the equation 3 O 2 (g)→2 O 3 (g) ΔH = +284.4 kJ, calculate ΔH for the following reaction. 3/2 O 2 (g) → O 3 (g). REMEMBER... O 2 is the most stable form of oxygen. So, it is equal to 0. Therefore, the the change in enthalpy is all about the product. (x products) - (0 reactants) = = X products = +284.4 kJ You can check using the table on P. 247 i

27. P. 247 The ΔH°f for O 3 (g) is +142.2 The ΔH°f for O 2 (g) is 0 Given the equation 3 O 2 (g)→2 O 3 (g) ΔH = +284.4 kJ There are two O 3 in the equation (142.2 kJ x 2 = 284.4 kJ) –we must remember the coefficients!!!! Then, the question asks us to calculate ΔH for the following reaction. 3/2 O 2 (g) → O 3 (g). There is only one O 3. Since 3/2 O 2 (g) → O 3 (g) is ½ of 3 O 2 (g)→2 O 3 (g) the enthalpy of the reaction will be ½ as well: ½ (+284.4kJ)...or +142.2kJ

28. Change of Enthalpy of Reaction The combustion of thiophene, C 4 H 4 S(l), a compound used in the manufacture of pharmaceuticals, produces carbon dioxide and sulfur dioxide gases and liquid water. The enthalpy change in the combustion of one mole of C 4 H 4 S(l) is -2523kJ. Use this information and data from Table 6.4 (p.247) to establish ΔH°f for C 4 H 4 S(l). STEP I: WRITE THE BALANCED EQUATION *To carry any combustion reaction you need oxygen as a reactant. Liquid water will always be included as one of the products. __ C 4 H 4 S(l) + ___ O 2 (g) → __ CO 2 (g) + ___ S0 2 (g) + ___ H 2 0(l) 1 6 41 2

29. Change of Enthalpy of Reaction The combustion of thiophene, C 4 H 4 S(l), a compound used in the manufacture of pharmaceuticals, produces carbon dioxide and sulfur dioxide gases and liquid water. The enthalpy change in the combustion of one mole of C 4 H 4 S(l) is -2523kJ. Use this information and data from Table 6.4 (p.247) to establish ΔH°f for C 4 H 4 S(l). STEP II: USE THE COEFFICIENTS FROM YOUR BALANCED EQUATION TO DETERMINE THE TOTAL CHANGE IN ENTHALPY IN THE FORMATION OF EVERY SUBSTANCE USED IN THE REACTION. USE THIS INFORMATION TO WRITE YOUR ΔH° RXN EQUATION. i

30. Change of Enthalpy of Reaction The combustion of thiophene, C 4 H 4 S(l), a compound used in the manufacture of pharmaceuticals, produces carbon dioxide and sulfur dioxide gases and liquid water. The enthalpy change in the combustion of one mole of C 4 H 4 S(l) is -2523kJ. Use this information and data from Table 6.4 (p.247) to establish ΔH°f for C 4 H 4 S(l). STEP II: i PRODUCTS 4 (________kJ/mol CO 2(g) ) 2 (________kJ/mol H 2 O (l) ) 1 (________kJ/mol SO 2(g) ) REACTANTS X kJ/mol C 4 H 4 S(l) 6 (________kJ/mol O 2(g) ) -393.5 -285.8 -296.80.00

31. Change of Enthalpy of Reaction The combustion of thiophene, C 4 H 4 S(l), a compound used in the manufacture of pharmaceuticals, produces carbon dioxide and sulfur dioxide gases and liquid water. The enthalpy change in the combustion of one mole of C 4 H 4 S(l) is -2523kJ. Use this information and data from Table 6.4 (p.247) to establish ΔH°f for C 4 H 4 S(l). STEP II: i [4(-393.5) + 1(-296.8) + 2(-285.8)] – [1(ΔH) + 6(0)] = -2523 PRODUCTS － REACTANTS = ΔH RXN

32. Change of Enthalpy of Reaction The combustion of thiophene, C 4 H 4 S(l), a compound used in the manufacture of pharmaceuticals, produces carbon dioxide and sulfur dioxide gases and liquid water. The enthalpy change in the combustion of one mole of C 4 H 4 S(l) is -2523kJ. Use this information and data from Table 6.4 (p.247) to establish ΔH°f for C 4 H 4 S(l). STEP III: SOLVE for "X" i -2442.4 - ΔH(reactants) = -2523 ΔH C 4 H 4 S(l) = 81.3kJ/mol

33. CHANGE IN H

34. Change in Enthalpy in a multi-step reaction

36. CHEMICAL EQUILIBRIA

37. Things to remember This is how you convert an Equilibrium constant from K c to K p : Kp = Kc (0.0821 T)^Δn Δn is the sum of all stoichiometric coefficients belonging to products minus the sum of all stoichiometric coefficients belonging to reactants T is the temperature during the reaction in Kelvin. Remember that Kelvin has exactly the same degree of difference between integers as celsius, but it does have a different starting point. Kelvin's zero is 273° less than celsius. For example, 2° C is equal to 275° K. 27° C is equal to 300° K.

38. Qc and Kc Question h

39. EQUILIBRIUM of 2 or more RXN's If a reaction can be expressed as the sum of two or more reactions, the equilibrium constant for the overall reaction is given by the product of the equilibrium of the individual reactions. Kc = (K'c) (K"c)

40. Let me elaborate... 1st Step Reaction2nd Step Reaction Overall Reaction

41. To find the overall equilibrium of a multi-step reaction

42. 2 step reaction 1st step reaction N 2 (g) + O 2 (g) ↔ 2 NO(g) Kc 1 = 2.3 x 10^-19 2nd step reaction 2 NO(g) + O 2 (g) ↔ 2 NO2(g) Kc 2 = 3 x 10^6 Kc = Kc 1 x Kc 2 = (2.3 x 10^-19)(3 x 10^6) Kc = 7 x 10^-13 Write the equilibrium equation for this multi-step reaction:

43. CHEMICAL KINETICS Reaction rates...

44. N2 + 3H 2 → 2NH 3 Molecular hydrogen reacts at a rate of 0.074 M/s Suppose that at a particular moment during the reaction molecular hydrogen is reacting at the rate of 0.074 M/s. a) At what rate is ammonia being formed? b) At what rate is molecular nitrogen reacting?

45. N2 + 3H 2 → 2NH 3 Molecular hydrogen reacts at a rate of 0.074 M/s At what rate is ammonia being formed? _ - _ GIVEN

46. N2 + 3H 2 → 2NH 3 Molecular hydrogen reacts at a rate of 0.074 M/s At what rate is molecular nitrogen reacting? - GIVEN -

47. Describe the difference between Heat of solution and Heat of dilution. Give an example of each one.

48. Heat of solution is the amount of heat absorbed or released during the act of combining a solute with a solvent. An example is adding salt to water. There are two steps to this process: the Lattice Energy (breaking down the molecules) and the heat of hydration (where the ionically charged particles dissolve by attracting to the dipole water molecules. Heat of dilution refers to the amount of heat absorbed or released when water is added to a solution already made. In this latter case, if the act of making a solution is exothermic, adding more water will make it even more exothermic (hotter). For example, as you add more and more water to a solution of sulfuric acid and water, the more heat it releases (the more it burns).

49. Neutralization Explain how you would neutralize an acid and a base: Mix an acidic solution with a basic solution wherein the ratio of H+ ions to OH- ions equal to 1.

50. Cabbage Juice as a pH indicator Explain how cabbage juice works as a pH indicator: There is anthocyanin in cabbage juice. Anthocyanin reacts with hydroxyl ions (OH-). Hydroxyl ions jump off anthocyanin when in an acidic solution, thereby changing the chemical composition of the anthocyanin (the pH indicator). This will cause the juice to react with light differently than if these OH- ions had not jumped off the anthocyanin (makes the juice turn a reddish color). Conversely, Hydroxyl ions will jump from the solution onto the anthrocyanin molecules when there is an excess of them in the solution (such as when cabbage juice is mixed with a basic solution). This causes the juice (the pH indicator) to turn a yellowish color.

51. NOT mentioned... Balancing redox reactions Kw Ka Kb pH the galvanic cell KNOW THESE CONCEPTS!!!!!!!!!!!