WORKSHEET #1. Dougherty Valley HS AP Chemistry Hess s Law Problems

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1 Dougherty Valley HS AP Chemistry Hess s Law Problems WORKSHEET #1 1. Calculate the standard enthalpy change, ΔH o, for the formation of 1 mol of strontium carbonate (the material that gives the red color in fireworks) from its elements. ( 10 KJ) Sr (s) Theinformation available is (1) () () Sr (s) SrO (s) C(graphite) 1 C(graphite) O O O SrO (s) Sr (s) Sr (s) H H H - 59 kj - kj - 9 kj. 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 (+ 15. kj) C (s) Determine thestandard enthalpy change for this reaction from the following standard enthalpies of reaction : (1) () () C(s) CH The next one is challenging! H O H O HO H O CH H H H. One reaction involved in the conversion of iron ore to the metal is ( 11 kj) FeO (s) (1) Fe O (s) () Fe O (s) of iron oxides with : Fe(s) Fe O Fe(s) FeO (s) (s) H H H 11. kj - 1. kj 06.1 kj Calculate thestandard enthalpy change for this reaction from these reactions () Fe O (s) H H H - 7 kj - 5 kj 19 kj

2 [] Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values: PCl 5 PCl + Cl P (s) + 6Cl PCl PCl 5 P (s) + 10Cl Answer = 9.8 kj ΔH = 9 kj ΔH = 8 kj [5] Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values: + H O C H + O C H + H C H 6 H O H + O C H 6 + O + H O Answer = 5 kj ΔH = 9.5 kj ΔH = 71. kj ΔH = 8 kj [6] Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values: N H (l) + H NH N H (l) + CH O(l) CH O + N + H N + H NH CH O(l) CH O + H Answer = 18 kj ΔH = 7 kj ΔH = 6 kj ΔH = 65 kj [7] Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values: H SO (l) SO + H O H S + O H SO (l) H S + O SO + H O(l) H O(l) H O Answer = 7 kj ΔH = 5.5 kj ΔH = 07 kj ΔH = kj [8] Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values: C H O(l) + H O(l) C H 6 O(l) + O C H 6 O(l) + O + H O(l) C H O(l) + O + H O(l) Answer = 0.0 kj ΔH = kj ΔH = 58.5 kj [9] Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values: N + O NO N + H NH NH + H O(l) NO + 7H H O(l) H + O Answer = 8 kj ΔH = 115 kj ΔH = 1.5 kj ΔH =.7 kj [10] Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values: C(s) + O H O(l) H + O C H 6 C(s) + H + H O(l) C H 6 + O Answer = 886 kj ΔH = 6 kj ΔH = kj ΔH = kj

3 [11] Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values: N H (l) + CH O(l) CH O + N + H NH N H (l) + H NH N + H CH O + H CH O(l) Answer = 6. kj ΔH =.5 kj ΔH = 57.5 kj ΔH = 81. kj [1] Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values: H + Cl HCl Cl + H O(l) CH Cl (l) + O HCl + O H O(l) + Cl CH Cl (l) + H + O Cl + H O(l) Answer = 0 kj ΔH = 7.5 kj ΔH = 105 kj ΔH = 0.5 kj [1] Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values: C H + O + H O C H 6 C H + H H + O H O + H O C H 6 + O Answer = 705 kj ΔH = 8.5 kj ΔH = 1.7 kj ΔH = 89 kj [1] Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values: HCl + NaNO (s) HNO (l) + NaCl(s) NaCl(s) + H O(l) HCl + Na O(s) NO + NO + Na O(s) NaNO (s) NO + NO N O + O HNO (l) N O + O + H O(l) Answer = 78 kj ΔH = 507 kj ΔH = 7 kj ΔH = kj ΔH = kj [15] Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values: Zn(s) + S 8 (s) + O ZnSO (s) Zn(s) + S 8 (s) ZnS(s) ZnS(s) + O ZnO(s) + SO SO + O SO ZnO(s) + SO ZnSO (s) Answer = kj ΔH = 18.9 kj ΔH = 97.5 kj ΔH = kj ΔH = 0. kj These problems involve using heat of formation values that are found in the appendix of your textbook. [16] What is the enthalpy of the following reactions? Use equation from Equation Sheet [Products minus reactants] (a) SiF Si(s) + F (b) SiF Si + F (c) SO + H O H SO (aq) (d) K O (s) + H O(l) 6KOH(aq) + O (e) Fe O (s) + 8HCl FeCl (s) + FeCl (s) + H O SiF - H f = KJ/mol FeCl - H f = 1.8 KJ/mol FeCl - H f = 99.5 KJ/mol Fe O - H f = KJ/mol SO - H f = 5.5 KJ/mol Si - H f = 50 KJ/mol

4 Dougherty Valley HS AP Chemistry Enthalpies of Formation Practice WORKSHEET # Directions: use your textbooks appendix to calculate the standard enthalpy change for each of the following reactions using heats of formation. Must show all work to receive credit. These are from another textbook, H f values may be a bit different. (5.71) [1] SO + O SO (196.6 kj) [] Mg(OH) (s) MgO(s) + H O(l) (7.1 kj) [] N O + H N + H O (976.9 kj) [] SiCl (l) + H O(l) SiO (s) + HCl (68. kj) (5.7) [5] HBr + O H O(l) + Br (l) (6.7 kj) [6] NaOH(s) + SO Na SO (s) + H O (8.5 kj) [7] CH + Cl CCl (l) + HCl (.7 kj) [8] Fe O (s) + HCl FeCl (s) + H O (150 kj)

5 PRACTICE TEST/THERMOCHEMISTRY/AP CHEMISTRY 1. a) Calculate the amount of heat transferred when g of NO is formed by the following reaction: N + O NO ΔHrxn = +16. kj b) Draw an energy diagram for this process.. Predict the value for ΔH f for the following scenarios: a) Br b) Br(l) c) I d) I(s). Calculate the ΔHrxn for the following reaction: CH + O + HO(l) ΔH f CH = 6.6 kj/mol ΔH f = -9.5 kj/mol ΔH f HO(l) = kj/mol. A 5.00 g sample of liquid water at 5.0 C is heated by the addition of 8.0 J of energy. The final temperature of the water is C. The specific heat capacity of the liquid is.18 J/g C. a) -1 b).0 c) 5. d) 95. e) This problem was taken directly from the 1995 AP chem. exam. Propane is a hydrocarbon that is commonly used as a fuel for cooking. Propane s formula is CH8. a) Write a balanced equation for the complete combustion of propane gas. b) Calculate the volume of air at 0 C and 1.00 atm that is needed to burn completely 10.0 g of propane. Assume that air is 1.0% O by volume. c) The heat of combustion (ΔH combustion ) is -,0.1 kj/mol. Calculate the heat of formation, ΔH f, of propane given that ΔH f of HO(l) is -85. kj/mol and ΔH f of is -9.5 kj/mol. d) Assuming that all of the heat evolved burning 10.0 g propane is transferred to 8.00 kg of water (specific heat =.18 J/g C), calculate the increase in temperature of the water.

6 AP Chemistry Thermochem FRQs 00 00B. 006

7 005B Skip part (d) for now.