A 0.4485 g sample of pewter, containing tin, lead, copper, and zinc, was dissolved in acid. Tin was precipitated as SnO2·4H2O and removed by filtration. The resulting filtrate and washings were diluted to a total volume of 250.0 mL. A 15.00 mL aliquot of this solution was buffered, and titration of the lead, copper, and zinc in solution required 34.07 mL of 0.001534 M EDTA. Thiosulfate was used to mask the copper in a second 20.00 mL aliquot. Titration of the lead and zinc in this aliquot required 34.56 mL of the EDTA solution. Finally, cyanide was used to mask the copper and the zinc in a third 25.00 mL aliquot. Titration of the lead in this aliquot required 25.76 mL of the EDTA solution. Determine the percent composition by mass of each metal in the pewter sample.

Cu%=

Zn%=

Pb%=

Sn%=

1. What is the molarity of a 12.6% solution of sodium carbonate with a density of 1.31 g/mL?

2. What is the mass percent of potassium iodide in a 2.89 M solution of KI with a density of 1.27 g/mL?

3. In an experiment similar to your 15.72 mL of a 0.1294 M Ba(OH)2 solution is titrated with 20.00 mL of a HNO3 solution. What is the molarityof the HNO3?

A galvanic cell is prepared using 0.150 M Co2+ and a cobalt electrode as one half-cell and 0.0350 M Ag+ and a silver electrode as the other half-cell.

1.) Write the reduction forms of the equation for the anodic half-reaction and the cathodic half-reaction

2.) Write the net ionic equation for the overall cell reaction. Ensure that your equation shows the spontaneous reaction direction.

3.) Calculate Ecell

Write all of the possible term symbols for an excited carbon atom with an electron configuration of 1s²2s²2p¹4f¹. Include the J values on any D terms

Consider the cell described below at 251 K:

Pb | Pb²⁺ (1.47 M) || Fe³⁺ (2.11 M) | Fe

Given the standard reduction potentials found on the sheet attached to the exam, calculate the cell potential after the reaction has operated long enough for the [Fe³⁺] to have changed by 1.078 M

Can carbon be made into a semiconductor? EXPLAIN

In an experiment, I mix 10ml 0.1M Cd(NO3)2 and 10ml 0.1M Na2C2O4, then I titrate the mixture with 5M NH3. The total volume of solution after titration is9.10ml. The Ksp value of CdC2O4 is 3.22x10^-9

I need to do the following: I have no idea how to do them, please help. Thanks.

Total moles of (C2O4) 2-

total moles of (Cd) 2+

Moles of NH3 that did not react with (Cd) 2+

Molarity of NH3 that did not react with (Cd) 2+

1)

A geological sample is found to have a Pb-206/U-238 mass ratio of 0.337/1.00. Assuming there was no Pb-206 present when the sample was formed, how old is it? The half-life of U-238 is 4.5 × 10⁹ years.

A geological sample is found to have a Pb-206/U-238 mass ratio of 0.337/1.00. Assuming there was no Pb-206 present when the sample was formed, how old is it? The half-life of U-238 is 4.5 × 10⁹ years.

one stage of nuclear reprocessing involves dissolving the spent fuel rods in nitric acid to produce uranyl nitrate. An organophosphorus liquid, tributyl phosphate, is then used to extract the uranyl nitrate from the water. The two liquids are highly immiscible (1 mL tributyl phosphate/ 165 mL water). We would like to remove 90% of the uranyl nitrate from 2 kg of a 20 wt% aqueous solution. How much tributyl phosphate is required for thie process if we use 3 stages in a cross-current congifuaration? How much is needed if the three stages are operated in a counter-current configuration? why is there a difference in the amount of solvent needed for the two configurations? You can assume the distribution coeffiecent on a solute-free basis is 5.5

Consider a voltaic cell constructed from the following redox couples and make the following predictions about what would occur if you ran this cell under standard conditions.

couple

Pb2+ | Pb Ce4+, Ce3+ | Pt

reduction half reaction

Pb2+ + 2 e- <==> Pb Ce4+ + e- <==> Ce3+

reduction potential E ?re

- 0.13 volts + 1.44 volts

(a) Write the anode, cathode and overall cell reactions.

(b) Calculate the ideal cell voltage, E ?cell, for this voltaic cell.

A certain weak acid, HA, with a Ka value of 5.61�10?6, is titrated with NaOH.

A) A solution is made by titrating 7.00mmol (millimoles) of HA and 2.00mmol of the strong base. What is the resulting pH?

B) More strong base is added until the equivalence point is reached. What is the pH of this solution at the equivalence point if the total volume is 38.0mL ?

WILL RATE IF BOTH ANSWERS ARE CORRECT WITH STEPS SHOWN

A.) What is the pH of a buffer prepared by adding 0.607 mol of the weak acid HA to 0.406 mol of NaA in 2.00 L of solution? The dissociation constant Ka of HA is 5.66×10−7. ANSWER IS: 6.072

B.) What is the pH after 0.150 mol of HCl is added to the buffer from Part A? Assume no volume change on the addition of the acid. ANSWER IS: 5.776

C.) What is the pH after 0.195 mol of NaOH is added to the buffer from Part A? Assume no volume change on the addition of the base.

I had to request the answer for part B but I don't know how to work the problem out. Please help me!

Transferrin is the iron-transport protein found in blood. It has a molecular mass of 81000 and carries two Fe³⁺ ions. Desferrioxamine B is potent iron chelator used to treat patient with iron overload. It has a molecular mass of 650 and can bind one Fe³⁺. Desferrioxamine can take iron from many sites within the body and is excreted (with its iron) through the kidneys. The molar absorptivities of these compounds are given in the following table. Both compounds are colorless (no visible absorption) in the absence of iron.

                                                               e (M^-1 cm^-1)                    

l (nm)                           Transferrin            Desferrioxamine

428                          3540                   2730

470                          4170                   2290       

  (a) A solution of transferrin has an absorbance of 0.463 at 470 nm in a 1.000 cm cell. Find the concentration of transferrin in mg/mL and the concentration of iron in μg/mL.

(b) After addition of desferrioxamine (which dilutes the sample), the absorbance at 470 nm was 0.424 and the absorbance at 428 nm was 0.401. Calculate the fraction of iron in transferrin. Remember that transferrin binds two Fe³⁺ ions and desferrioxamine binds only one.

4. The enzyme alcohol dehydrogenase catalyzes the oxidation of ethyl alcohol by NAD+ to give acetaldehyde plus NADH and a proton:

CH3CH2OH + NAD+                  CH3CHO + NADH + H+

The rate of this reaction can be measured by following the change in pH. The reaction is run in 1 mL 10 mM TRIS buffer at pH 8.6. If the pH of the reaction solution falls to 8.4 after ten minutes, what is the rate of alcohol oxidation, expressed as nanomoles of ethanol oxidized per mL per sec of reaction mixture?