ch. 15, 14, 10  solution & thermodynamics

1. Describe how to prepare a 275 mL of a 25.0 mM sucrose (C12H22O11) solution using [10 points]

a. solid sucrose and water

b. 85 mM sucrose solution and water

2. 15 mL of a 25 mM KOH was needed to titrate 55 mL of a H2SO4 solution. What is the [H2SO4] ? [10 points]

3. Excess sodium carbonate (Na2CO3) was added to 25 mL solution containing silver nitrate (AgNO3), which formed 1.0 grams of a precipitate. What is the [Ag +] (prior to adding sodium carbonate) ? [10 points]

4. fill-in the below table: positive or negative ? [10 points]

 Rx happens ? ∆ G ∆ H ∆ S Yes; always No; always Yes @ low T No @ high T Yes @ high T No @ low T

5. Freon-11:

Chemical formula = CCl3F      Specific heat

Boiling point = 24 °C                   Gas = 0.56 J / g K

Freezing point = - 75 °C               Liquid = 0.87 J / g K

Solid = 0.72 J / g K

dHvap = 24.75 kJ / mol          dHfus = 15.0 kJ / mol

calculate the heat needed to change 15.0 grams of Freon-11 at – 55 °C to 35 °C ? [15 points]

6. state the sign (i.e. positive, negative, or ambiguous) of ∆S in the following reactions. If it is ambiguous, then give your reason(s). [10 points]

a. NaCl (s) -->  Na + (aq) + Cl - (aq) ; ∆S is _________

b. Mg (s) + O2 (g) -->  MgO (s) ; ∆S is _________

c. C2H6 (g) + O2 (g) -->  CO2 (g) + H2O (g) ; ∆S is _________