Chemistry Weekly Homework

Weekly HW #13

1. What is the pH of an aqueous solution of 0.241M Alloxanic acid pK_a= 6.64?

• The following initial rate data are for the Oxidation of Plumbate ion by Molybdenum (IV) ion in aqueous solution:    

PbO₃^3- + 2 Mo⁴⁺ + H₂O –> PbO₄^3- + 2 Mo³⁺ + 2 H⁺ 

Experiment	[PbO33-]o, M	[Mo4+]o, M	Initial Rate, Ms-1
EXPERIMENT 1	0.270	0.243	5.01E-06
EXPERIMENT 2	0.540	0.243	4.01E-05
EXPERIMENT 3	0.270	0.1215	1.25E-06
EXPERIMENT 4	0.540	0.486	1.60E-04

What is the determined Rate Law for the above reaction, including the value of the rate constant k?

3) The half-life for the 1^st order decay of a neurotoxin is found to be 2.5 hrs.  If a patient reports to have ingested a initial quantity equivalent to 200 uM of toxin into the blood, how long would one need to wait before the level dropped to an acceptable level of 1.0 uM?  

4) 100ml of 0.100M Sulfuric Acid(H₂SO₄) is added to 200ml of 0.15M Barium Hydroxide (Ba(OH)₂),

what is the resulting pH? 

5) What is the nuclear reaction responsible for the initial formation of Carbon-14 in the upper atmosphere? (one line) 

6) 10ml of 0.1M Nitric Acid is added to 20ml of 0.2M Sulfuric (H₂SO₄) and then diluted up to 100 ml, what is the resulting pH?  Hint: Recall [H3O+] = total moles of [H+]/total Volume

7) Which of the following acid solutions is the MOST acidic? (careful it’s a mix of concentrations as well as Ka and pKa)

a) 1.0M Phenol, K_a = 1.3 x 10^-10                               b) 0.08M Pyruvic acid, pK_a = 2.76

c) 0.1M Bromo-Acetic acid  pKa = 4.75                               d) 0.01M Chloro-Nitrous acid, K_a = 4.5 x 10^-3

8) Based upon the assigned video, what is required WITHIN the cell for the cell to distinguish a virus from necessary proteins.  (1-3 words)

9) Five plots, labeled A) – E) are shown below. What can be obtained from each of these plots?

				PLOT LABEL
				A,B,C,D,E
The slope of the line tangent to the curve at t = 0 is the initial rate of the reaction.
The activation energy can be obtained from the product of the slope of the line and R.
The rate constant for a zero order reaction can be obtained from the slope of the line.
The rate constant for a second order reaction can be obtained from the slope of the line.
The rate constant for a first order reaction can be obtained from the slope of the line.

10) Calculate the pH of a 0.252 M aqueous solution of Diethylamine ((C₂H₅)₂NH, pK_b=4.20)

11) True or False: The pK_w of water is always 14.0 (which statement(s) below are relevant)

1. False because all equilibria are temperature dependent
2. True because it is the basis for the dissociation of water and pH
3. False because pH is only true for water and not organics
4. False because pK_w is based on two temperature dependent variables k_f and k_b
5. True because the pH plus pOH always sum to 14.0

The Reaction:            2X2 (gas) + Y2(gas)  < == >  2Z2(gas) is found to be ENDOTHERMIC and have a Kpeq=  7.5 x 10-3 atmospheres at 300K

12) What would be the K_c for this reaction at 300K for above reaction?

13) If the temperature where increase what would happen to the equilibrium concentration for above reaction?

14) How much 0.100M solution of Nitric Acid is needed to bring 22.1 ml of 0.150 M NaOH to Neutrality?

15) The Activation energy for the Li Ion battery is 51.2 kJ/mole.  If we assume that current is proportional to rate constant, what would be the percent loss of current for a battery cooled from 25^oC (78F) to 0^oC(32F).  Hint: Assume that k₁ is 100 for convenience

16) Consider the following equilibrium system:     PCl₅(g)  < == > PCl₃(g) + Cl₂(g)

A 10.00 L evacuated flask is filled with 0.4415 moles  PCl₅(g).  The temperature is then raised to 510.0 K, where the decomposition of PCl₅(g)  gas takes place to an appreciable extent. When equilibrium is established, the total pressure in the flask is 2.822 atm.   What is the value of the equilibrium constant in terms of concentrations, K_c, at 510.0 K?  

Consider the Following OVERALL Reaction conducted at 475K

A  +  B  < == >  C + 2D In which the Rate of the forward reaction is equal to                  Rf = kf [A] and the Rate of the reverse (backward) reaction is equal to     Rb = kb [C][D]2 /[ B]

17)  If AT EQUILIBRIUM, one finds that the concentrations of B and D are 0.135M, while the concentrations of A and  C are 0.0314 M and 0.0117 M respectively; What would be the NUMERIC VALUE of the Equilibrium Constant (K_c)?

18) Staring with these concentrations as defined above if one removed 0.0013 moles/L of C and add 0.0231 moles/L of D in this reaction; How would that change the Reaction Quotient Q. NUMERICALLY? 

19) And how would that shift the Overall Reaction (Left or Right) toward (Reactants or Products)?

20-21) What would the final concentration of [C] be after equilibrium is reestablished (SETUP ONLY)

Consider the Reaction Mechanism below:

                                                         Elementary Step (1)       X + W  è  C

                                                            Elementary Step (2)      C  + W è   2K

                                                           Elementary Step (3)       X + K è   Z

                                                           Elementary Step (4)     W + K è Y

22) What is the Net Reaction?

23) If the Second elementary step/reaction is found to be the slowest, what would be the rate law for this reaction?

24) Illustrate with the use of detailed diagram/graph how the Reaction Quotient is related to the time-dependent outcome of any chemical reaction (do this on answer sheet)