1)       One way to cool your 8 ounce morning cup of coffee is to plunge an ice-cold piece of aluminum into it.  Suppose you store a 20.0 g piece of aluminum in the refrigerator (4.4^oC), and then drop it into your coffee.  The coffee temperature drops from 90.0^oC to 55.0^oC.  How many kilojoules of energy were transferred?

2)       A 192 gram piece of copper was heated to 100oC in a boiling water bath, then dropped into a beaker containing750. mL of water at 4.0oC.  What is the final temperature of the copper and water after they reach thermal equilibrium? (Assume no heat is lost to the surroundings; c(Cu) = 0.385 J g^-1 K^-1)

3)       Lead has been known and used since ancient times.  To obtain the metal, the ore galena (PbS) is first heated in air to form PbO. 

2PbS(s) + 3O₂(g)  ®  2O(s) + 2SO₂(g)             DH = -827.4 kJ

The lead(II) oxide is then reduced using carbon.

PbO(s) + C(graphite)  ®  Pb(s) + CO(g)                DH = +106.8 kJ

To obtain the lead from 1.00 kg of pure PbS, how much heat is evolved or  required?  Is this process endo- or exo- thermic?

4)       The Romans used CaO as mortar in stone structures.  The CaO was mixed with water to give Ca(OH)₂ and this slowly reacted with CO₂ in the air to produce limestone.  

Ca(OH)₂(s) + CO₂(g)  ®  CaCO₃(s) + H₂O(g)

Calculate the enthalpy change for this reaction.

5)       Given the following chemical reactions, calculate the enthalpy of formation of MnO₂(s).

2MnO₂(s)  ®  2MnO(s) + O₂(g)      DH^o = + 264 kJ

MnO2(s) + Mn(s)  ®  2 MnO(s)      DH^o = -240. kJ

6)       One method of producing H₂ on a large scale is the following chemical cycle: 

SO₂(g) + 2 H₂O(g) + Br₂(g)  ®  H₂SO₄(l) + HBr(g)

H₂SO₄(l)  ®  H₂O(g) + SO₂(g) + ½ O₂(g)

2 HBr(g)  ®  H₂(g) + Br₂(g)

Using the table of standard enthalpies of formation in your book, calculate DH^o for each step.  What is the equation for the overall process and what is its enthalpy change?  Is the overall process endo- or exo- thermic?