When concentrated CaCl₂(aq) is added to a Na₂HPO₄(aq), white precipitate forms that is 38.7% Ca by mass. Write a net ionic equation representing the probable reaction that occurs.

Answer all questions in the space provided. Number each question in your response. Answer each question in no more than 100 words (words exceeding this limit will not be considered in grading). One or more of the following questions will be graded.

For this activity, the letter "D"=Delta

1. The methane, CH₄(g) reaction and associated thermodynamic data at 298 K are given below.

CH₄ (g) + 2 O₂ (g)CO₂ (g) + 2 H₂O (l)

DG^o_rxn= - 818kJ/mol

DH^o_rxn= - 890kJ/mol

DS^o_rxn= - 242 J/molK

Suppose that you start with 1 atm CH₄, 0.2 atm O₂, and 0.00038 atm CO₂. How does the maximum non-expansion work compare with standard conditions? Provide a thermodynamic justification to your answer.

2. Solid Ni metal (melting point 1728 K) has the amazing ability to react with gaseous carbon monoxide, CO(g), at 323 K to form a volatile, colorless liquid, Ni(CO)₄ (boiling point 316 K). Ludwig Mond - the person who made this discovery-described the reaction as 'giving wings to the metal'.

Ni (s)+4 CO (g)Ni(CO)4(g) DH^orxn= -161 kJ/mol

Given that DS^Orxn = -410 J/molK, calculate the value of DG^Orxn at 25^OC.

3. Considering the data above, and given that for the process Ni(s)Ni(g) DH^O_vap = +430 kJ/mol, determine the bond enthalpy for a Ni--CO bond.

4. Suppose that you place 1 atm of Ni(CO)4(g) in a closed container with a trace amount of CO (PCO=0.002 atm) at 25^OC and allow it to reach equilibrium. What changes, if any, do you expect to observe when the reaction mixture is allowed to reach equilibrium? Explain your reasoning.

5. Mond developed a practical two-step separation scheme to obtain pure nickel metal from a mixture of nickel with other metals that do not undergo the same reaction, using only carbon monoxide. If the first step involves formation of pure gaseous Ni(CO)4 from the mixture, based on the thermodynamic data above, what do you think might be the final step to obtain pure Ni metal? Use a thermodynamic argument to justify your answer.

6. Consider the evaporation of water at 298 K and 1 atm pressure, H₂O(l) -> H₂O(g). The standard free energy of this reaction is: DG^O_rxn = +8.6 KJ/mol. If the partial pressure of water in the air on a dry (non-humid) day at 298 K is 0.001 atm, calculate DG_rxn and state whether the above process (i.e. evaporation of water) would proceed spontaneously. Show how you arrived at your answer.