Ch. 10 & 15  thermodynamics & solution                   test       [85 points]

 

For problems involving calculations, show your work in an organized manner, include any relevant equation (or formula and conversion factor(s)), put the proper units in your calculations / answer, and have the proper number of significant figures in your answer.   

 

Academic Honesty:   The answers on this test are my own and I am using only the allowed set of notes as described in the syllabus.  I have not discussed the test questions with anyone before or during the test nor have I seen the test questions prior to the exam.  If you violate any of the preceding items or do not sign, your semester grade is a F.

 

                                                                                                Signature:  ___________________

  1.  What is ΔS in the below situations (i.e. ΔS > 0; ΔS < 0; ΔS 0; ambiguous); justify / rationalize your response.  [15 points]

 a. Mix aqueous solutions of silver nitrate and sodium chloride

 

 

 b.  Dissolve magnesium chloride in water

 

 

 c.  Melting of ice

 

 

 

 

 2.  Referring to the change in Gibbs’ free energy, justify / rationalize that the melting of ice depends on temperature; include a description of this temperature dependence.  [10 points]


 3.  What is the change in temperature due to the addition of 1.5 grams of potassium hydroxide in 75 mL of water ?  [15 points]

 

 4.  How much heat is needed to change 10.0 grams of water at 0 °C to water at 75 °C ?  [15 points]


 5.  Describe how to prepare a 500.0 mL aqueous solution of 25.0 mM calcium chloride using  ___.  [10 points]

 

 a.  Solid calcium chloride and water

 

       b.  75.0 mM calcium chloride solution

 

 

 6. Excess sodium sulfide was added to a 35.0 mL aqueous solution of silver nitrate, which formed 1.5 g of a precipitate.  Based on the preceding information, determine the concentration of silver nitrate prior to the addition of sodium sulfide.  [10 points]

 

 

 7.  In regards to a 25.0 % NaCl solution, what is the  ___ of NaCl ?  Assume the solution’s density is 1.19 g / mL.  [10 points]

 

a.  Molarity

 

      b.  Mole fraction