Name:

2. Based on your experience, when ice melts to a liquid is the process
    exothermic or endothermic?
Choose One Exothermic Endothermic

    When liquid water freezes to ice at 0 ^oC is this exothermic or
    endothermic? 
Choose One Exothermic Endothermic

11. A 2-in. piece of a two-layer chocolate cake with frosting provides
    1670 kJ of energy. What is this in Calories?

15. 74.8 J of heat is required to raise the temperature of 18.69 g of
     silver from 10.0 to 27.0 ^oC. What is the specific heat of silver?

17. Which requires more heat to warm from 22 ^oC to 85 ^oC, 50.0 g of
     water or 100. g of ethylene glycol (specific heat is 2.39 J/g ^oC)

27. A 150.0 g sample of metal at 80.0 ^oC is placed into 150.0 g of
     water at 20.0 ^oC. The temperature of the final system (metal and
     water) is 23.3 ^oC. What is the specific heat of the metal?

29. The heat energy required to melt 1.00 g of ice at 0 ^oC is 333J.
     If one ice cube has a mass of 62.0 g, and a tray of ice cubes
     contains 16 cubes, what quantity of energy is required to melt a
     tray of ice cubes at 0 ^oC?

35. Nitrogen monoxide has recently been found to be involved in a wide
     range of biological processes. The gas reacts with oxygen to give
     brown NO2 gas.

2NO(g)  +  O₂ --> 2NO₂        [delta]H^o = -114.1 kJ

     Is the reaction exothermic or endothermic? If 1.25 g of NO is
     completely converted to NO₂, what quantity of heat is evolved
     or absorbed?

39. Methanol, CH₃OH, is a possible automobile fuel. The alcohol
     produces energy in a combustion reaction with O₂.

2CH₃OH  +  5O₂ --> 2CO₂ +  4H₂O

     A 0.115 g sample of methanol evolves 1110 J when burned at
     constant pressure. What is the enthalpy change, [delts]H^orxn
     for the reaction? What is the enthalpy change per mole of methanol?

42. Calculate the enthalpy change, [delta]H^o, for the formation of
     1 mol of strontium carbonate (the material that gives the red color
     in fireworks) from its elements?

Sr  +  C  +  3/2O₂  -->  SrCO₃

     The experimental information available is:
     Sr  +  1/2O₂  --> SrO         [delts]H_f = -592 kJ
     SrO  +  CO₂  -->  SrCO₃     [delts]H_f = -234 kJ
     C  +  O₂  -->  CO₂            [delta]H_f = -394 kJ

44. Suppose you wish to know the enthalpy change for the formation of
     liquid PCl₃ from the elements

P₄  +  6CL₂  -->  4PCl₃        [delta]H_f = ?

     This reaction cannot be carried out directly. Instead, the enthalpy
     change for the reaction can be determined experimentally.

     P₄  +  10Cl₂  -->  4 PCl₃        [delts]H_rxn = -1774.0 kJ
     PCl₃  +  Cl₂  --> PCl₅            [delts]H_rxn = -123.8 kJ

     Use this information to calculate the enthalpy change for the
     formation of 1 mol of PCl₃ from P₄ and Cl₂.

45. The standard molar enthalpy of formation of solid chromium(III)
     oxide is -1139.7kJ/mol. Write the balanced equations for which the
     enthalpy of reaction is -1139.7kJ?

49. Enthalpy changes have been determined experimentally for the
     following reactions:

     Pb  +  Cl₂  -->  PbCl₂            [delta]H_f = -359.4 kJ
     Pb  +  2Cl₂ -->  PbCl₄           [delta]H_f = -329.3 kJ

     What is the enthalpy change for the reaction of lead(II) chloride
     chlorine to give lead(IV) chloride?

     PbCl₂  +  Cl₂  -->  PbCl₄        [delta]H_rxn = ?

63. Assume you mix 100.0 ml of 0.200 M CsOH with 50.0 ml of 0.400M
     HCl in a coffee cup calorimeter. The following reaction occurs:

CsOH  +  HCl  -->  CsCl  + H₂O

     The temperature of the solutions before mixing was 22.0 ^oC and it
     rises to 24.28 ^oC after the acid-base reaction. What is the enthalpy
     of reaction per mole of CsOH? (Assume that the densities of all
     solutions are 1.00 g/ml)

69. The meals-ready-to-eat (MRE) in the military can be heated on a
     flameless heater. Assume the reaction in the heater is:

Mg  +  H₂O  -->  Mg(OH)₂  +  H₂

     Calculate the enthalpy change under standard conditions (in joules)
     for this reaction. What quantity of Mg is needed to supply the heat
     required to warm 25 ml of water (d = 1.00 g/ml) from 25 to 85 ^oC?

79. One method of producing H₂ on a large scale is the chemical cycle
     shown here:

     step 1:     SO₂  +  2H₂O  + Br₂ --> H₂SO₄  +  2HBr
     step 2:     H₂SO₄  -->  H₂O  +  SO₂  +  1/2O₂
     step 3:     2HBr  -->  H₂  +  Br₂

     Using the table of standard enthalpies of formation in Appendix K,
     calculate [delta]H for each step. What is the equation for the overall
     process, and what is its enthalpy change? Is the overall process
     exothermic or endothermic?