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

dH_vap = 24.75 kJ / mol          dH_fus = 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) + O_{2 (g)} -->  MgO _(s) ; ∆S is _________

c. C₂H_{6 (g)} + O_{2 (g)} -->  CO_{2 (g)} + H₂O _(g) ; ∆S is _________