Nyb Fall 06 Unit Test 2

Class Test 2 202-NYB-05 Fall 2006 Instructor: Michael Lautman Blue

Name: ID:

1. a) Classify the following solutions in order of DECREASING freezing point.

SOLUTION 0.1 M HCl Water 0.05 M BaCl2 0.075 M K3PO4

RANK

b) Classify each of the following compounds as a strong electrolyte, a weak electrolyte or a non-electrolyte when dissolved in water. In addition, indicate whether it is acidic, basic or neutral.

Compound FeCl3 NH4I Ba(CH3COO-)2 NaHCO3

Electrolyte?

Acid/Base/Neutral

2. Given the list of metals and solutions below, predict which of the following reactions will occur spontaneously using the table of half cell potentials provided. Write the half reaction for each spontaneous reaction, and indicate the reducing agent. Metals: Mg, Al, Ag, Li, Cu Solutions: AgNO3(aq), ZnCl2(aq)

3. Botox® is a popular non-surgerical cosmetic procedure. The treatment involves the injection of Botulinum Toxin A below the skin in order to reduce the appearance of wrinkles. Botulinum toxin is the most deadly poisons known. The estimated lethal dose in humans is 200-300 pg/kg of body weight (pg= picogram = 1x10 -12g). In contrast, strychnine (rat poison) has a lethal dose of 1mg/kg of body weight. This means that botulinum toxin is nearly one billion times more toxic than rat poison. A researcher dissolves a 30.4 mg sample of botulinum toxin in 2.50 mL of water at 5.0 C. The solution has an osmotic pressure of 0.00195 atm. What is the molar mass of botulinum toxin? R=0.0821 atm L/mol K o

4. Barium hydroxide has a Ksp of 2.55 x 10-4 at 25oC. Calculate the solubility of barium hydroxide in a 0.02M solution of barium nitrate, and determine the pH of the resulting solution.

5. The following data were collected and plotted for the equilibrium Fe3+(aq) + SCN-(aq) ↔ [FeSCN]2+

[FeSCN]2+

Absorbance at 447 nm

4.10 × 10−5

0.161

9.60 × 10−5

0.402

2.00 × 10−4

0.818

2.92 × 10−4

1.24

3.82 × 10−4

1.64

Absorbance vs. Concentration y = 4323.7x - 0.022 Absorbance

2 1.5 1 0.5 0 0

0.0001 0.0002 0.0003 0.0004 0.0005 [FeSCN2+] (mol/L)

A student prepares a solution using 10 mL of a 0.1M solution of iron(III) nitrate and 8 mL of a solution of sodium thiocyanate. The student measures the absorbance and finds it to be 0.500. Using the standard curve provided, determine the equilibrium concentration of [FeSCN]2+, Fe3+, SCN- and calculate Keq.