The laboratory reports that the concentration of ammonia as nitrogen in a sample is 3.4 mg/l. The pH value of the sample is 5.5 units. In what form is almost all of this ammonia? could this sample be toxic to aquatic organisms?

Assume you dissolve 0.235 g of the weak acid benzoic acid, C₆H₅CO₂H, in enough water to make 9.00 ✕ 10² mL of solution and then titrate the solution with 0.153 M NaOH.

C₆H₅CO₂H(aq) + OH^-(aq) C₆H₅CO₂^-(aq) + H₂O(ℓ)

What are the concentrations of the following ions at the equivalence point?

Na⁺, H₃O⁺, OH^-

C₆H₅CO₂^-

M Na⁺

M H₃O⁺

M OH^-

M C₆H₅CO₂^-

What is the pH of the solution?

Select the reactions for which we should expect a delta S (entropy) to be >0. Can select more than one.

CO2 (g) + 2H2 (g)-->CH3OH (l)

2SO2 (g) + O2 (g)--> 2SO3 (g)

Ba(OH)2 (s)-->BaO (s)+ H2O (g)

FeCl2 (s) + H2(g)-->Fe (s)+2HCl (g)

Suppose we have a solution of lead nitrate, Pb(NO3)2(aq). A solution of NaCl(aq) is added slowly until no further precipitation occurs. The precipitate is collected by filtration, dried, and weighed. A total of 11.72 g of PbCl2(s) is obtained from 200.0 mL of the original solution. Calculate the molarity of the Pb(NO3)2(aq) solution.

You have a one liter solution of kerosene containing 25 wt% propionic acid, add one liter of water, mix thoroughly and allow the two phases to settle. At this temperature, the distribution coefficient for propionic acid is 0.175 mass fraction in kerosene/mass fraction in water. What is the expected composition (wt%) and mass (kg) of the two phases? You may need to acquire physical properties for some of your species.

A solution is made by dissolving 40.0 g of KOH in 100 mL of water (density 0.995 g/mL) to form a solution. What is the mass percent solute in the solution?

1. 40.2%

2. 40.0%

3. 3.49%

4. 28.6%

5. 28.7%

25.0 g of water cooled 10 C to -20 C. Calculate the total Energy change.

With these useful numbers: ΔH fus = 334 J/g Δvap = 2260 J/g C_p for ice = 2.08 J/g ⁰C C_p for liquid water = 4.18 J/g ⁰C C_p for steam = 1.8 J/g ⁰C

Order: Vancomycin 12 mg/kg IV every 8 hours for an 11 year old child with a staph infection.

Supply: Vancomycin 500 mg vial to be reconstituted with 10 mL of sterile water. The child weighs 77 lb.

How many ml will you draw from the vial after reconstitution? _____________________

Order: Duricef oral solution 30 mg/kg PO bid for a 7 year old child with tonsillitis. The bottle of medication is labeled 250 mg per 5 mL. The child weighs 44 lb.

How many mL will you give? __________________

Order: Fragmin 80 units/kg SQ every 12 hours for unstable angina. The available dose is 10,000 units per mL.

The patient weighs 140 lb

How many mL will you give? _____________________

At 55.0 ?C, what is the vapor pressure of a solution prepared by dissolving 70.6g of LiF in 265g of water? The vapor pressure of water at 55.0 ?C is 118 mmHg. Assume complete dissociation of the solute.

The solvent for an organic reaction is prepared by mixing 60.0mL of acetone (C3H6O) with 59.0mLof ethyl acetate (C4H8O2). This mixture is stored at 25.0 ?C. The vapor pressure and the densities for the two pure components at 25.0 ?C are given in the following table. What is the vapor pressure of the stored mixture?

Write the complete electron configurations Cobal(Co) atom for its:

        1-its ground state
         2- an excited state       
2- Draw the orbital diagram for the complete electron configuration of Sulfur atom

3-Briefly explain how the following concepts are used in developing electron configuration of atoms: Hund’s rule and Pauli Exclusion principle.

2. Write the balanced chemical equation including states of matter, complete ionic reaction and net ionic reaction for the reaction between barium nitrate, Ba(NO3)2, and sodium chromate, Na2CrO4.
a. Balanced Chemical Equation
b. Complete Ionic Reaction
c. Spectator Ions
d. Net Ionic Reaction
3. Write a complete ionic reaction and a net ionic reaction for the following balanced chemical equation.
NaOH (aq) + C6H5COOH (aq)  H2O (l) + C6H5COONa (aq)       
4. Consult an internet resource for photographs of copper(I) oxide and of copper(II) oxide. Can one visually distinguish between these two compounds? Explain.   
Chemical Reactions and Equations p.14
5. Answer the following questions about the reaction:
S2-   +   NO3-    SO42-   +   NO  
a. Element oxidized    ___________
b. Element reduced    ___________
c. Reducing reactant    ___________
d. Oxidizing reactant    ___________

Trypsin and chymotrypsin are members of the family of serine proteases. They cleave peptide bonds at the C-terminal end of specific residues. Chymotrypsin recognizes aromatic residues, while trypsin recognizes lysine and arginine. The recognition of a particular side chain (side chain specificity) is fully determined by the structure and properties of the binding pocket. In the case of chymotyipsin the binding pocket is hydrophobic and is wide enough to accommodate an aromatic ring. Given what you know about the properties of Lys/Arg side chains, what can you say about the size/shape and possible interactions that would provide the substrate specificity in the case of trypsin? What amino acid residues from the trypsin molecule would you expect to find in the binding site?

Choose one of the transition or inner transition metals from the periodic table. (I choose Titanium) Using Chapter 23 of Chemistry, The Molecular Nature of Matter and Change, and Internet resources, discuss why your transition metal and their compounds display a variety of color. Be sure to include in your discussion, important oxidation states, the electron configuration and how the d-electrons are involved. How can you include the electromagnetic spectrum and the nature of light into your discussion? How is energy and wavelength related? Use your knowledge of the emission and absorption of light in your discussion. Remember to site your sources in APA style.

Are HCP metals typically more or less ductile than BCC metals? Why?