Part III (Plus answers to questions posted in the laboratory manual):

i) What are Q, [Ag+(aq)anode], and [Ag+(aq)cathode] when Emeasured becomes 0 mV for a concentration cell prepared from half cells having initial concentrations of 1.0 and 0.01 M. respectively?

ii) Assuming that both solution volumes were 10.0 mL for the concentration cell described in the above question, how much electricity (in coulombs) flowed from the time the circuit was completed until equilibrium was established?

Calculate the volume, in milliliters, of a 0.216 M NaOH solution that will completely neutralize each of the following: 1.) 3.71 mL of a 1.32 M HNO3 solution. 2.) 8.10 mL of a 0.800 M H3PO4 solution.

Complete combustion of 7.70 g of a hydrocarbon produced 23.6 g of CO2 and 11.3 g of H2O. What is the empirical formula for the hydrocarbon? Insert the subscripts:

CH

a) The reaction temperature for this lab is significantly above the boiling point of the solvent used (ethanol boils at 78 o C; the reaction mixture was heated up to 140 o C). Why are we able to conduct reactions above the boiling point of the solvent when using our microwave oven in lab?

b) Explain why hexane is a very poor choice as a solvent for a microwave reaction.

c) After developing a TLC plate, a student looks at the TLC plate under the UV lamp but cannot see any spots. What could the student have possibly done wrong? List three separate possible reasons for not being able to see any spots on a developed TLC plate.

d) After developing a TLC plate, a student looks at the TLC plate under the UV lamp but only sees large, overlapping blobs, instead of small spots. What is the likely problem, and what should the student do to obtain a better TLC?

The pKb values for the dibasic base B are pKb1 = 2.10 and pKb2 = 7.53. Calculate the pH at each of the following points in the titration of 50.0 mL of a 0.75 M B(aq) with 0.75 M HCl(aq).

(a) before addition of any HCl

(b) after addition of 25.0 mL of HCl

(c) after addition of 50.0 mL of HCl

(d) after addition of 75.0 mL of HCl

(e) after addition of 100.0 mL of HCl

500.0 mL of 0.140 M NaOH is added to 565 mL of 0.250 M weak acid (Ka = 8.39 × 10-5). What is the pH of the resulting buffer?

HA(aq)+OH^-(aq)=H2O(l)+ A^-(aq)

pH=?

The following takes place in a voltaic cell:
Zn(s) + Cu2+(1 M) → Cu(s) + Zn2+(1 M).
The cell has a voltage of +1.10 V.
Choose the answer that best relates to
questions 1-4.
(A) there is no change in the voltage
(B) the voltage becomes zero
(C) the voltage increases
(D) the voltage decreases, but stays
positive
(E) the voltage becomes negative
1. What happens to the voltage when a
saturated ZnSO4 solution is added to
the zinc compartment of the cell?
2. What happens to the cell voltage
when the copper electrode is made
smaller?
3. What happens to the cell voltage
when the salt bridge is filled with
deionized water instead of 1 M
KNO3?
4. What happens to the cell voltage
after the cell has operated for 10
minutes?

Could you please explain why?

A 500 mL buffer is usually prepared with 46 mM carbonic acid and 58 mM sodium bicarbonate. Unfortunately you have run out of these reagents; on hand you have the following: solid citric acid, disodium maleate (salt of maleic acid), benzylamine and hydrochloric acid. Which reagent(s), and how much of each, would you need to use to produce a 500 mL buffer with the same formal concentration and pH as the carbonic acid buffer

I calculated the original pH of the solution to be 6.452 and the original amount of moles to be 0.052.

What I'm stuck on is how to properly make a buffer without a strong conjugate for the colution

What problems can occur if the iodine value of a starting material is too low? And too high ?

Which of the following amino acids pairs would form the described hydrogen bond at pH 7? Explain your answer?

A. His Asp

B. Tyr His

C. Ser Arg

D. Glu Thr

A certain protein has a molecular weight of 250 kD. What is the approximate number of amino acids residues?

A. 2

B. 750

C. 1200

D. 2300

E. 27500

Identify the bonding in each of the following substances as ionic or covalent.

The odor of a dead fish is attributed to trimethylamine, (CH3)3N, one of a series of compounds of nitrogen, carbon, and hydrogen with a general formula of (CH3)_nNH_3-n where n = 0-3 (the n = 0 compound is ammonia).

a) The Kb of trimethylamine [(CH3)3N)] is 6.5E-5 at 25 C. Calculate the pH of 3.00nE-4 M solution of dimethylamine.

b) The Kb of mythylamine [(CH3)NH2] is 4.4E-4 at 25 C. Calculate the pH of 2.88E-3 M solution of mythylamine.

c) the Kb of dimethylamine [(CH3)2NH] is 5.9E-4 at 25 C. What concentration of dimethylamine is needed for the solution to have the same pH as the solution in part B?

(Combustion Analysis)

100 m3 of a fuel oil are burned per hour with 20 percent excess air in a steam generator. The fuel oil has a density of 926 kg/m3 and the following mass composition: 87% C, 12% H2, 1% S. Air enters the boiler at 100 kPa and 15 °C. Determine the following:

(a). The volumetric flow rate of the air (m3 /min) fed to the boiler;

(b). The flue gas molar composition on a dry basis, reporting all constituents to the nearest 0.001% and assuming complete combustion of the fuel oil; and

(c). The dew point temperature (°C) of the combustion flue gas, if the pressure exiting the boiler stack is 200 kPa.

(d). The mass flow rate of sulfur dioxide (SO2) emitted from the boiler, in metric tons per day, assuming complete combustion of the fuel oil.

Calculate the pH and pOH for the following solutions:

a) 0.0450 M NaOH

b) 0.160 M Ca(OH)2

c) a 1:1 mixture of 0.0125 M HCl and 0.0125 M Ca(OH)2

d) a 2:3 mixture of 0.0125 M HNO3 and 0.0125 M KOH