Data Tables:

Post lab Questions (written or type out on a separate sheet):

(Q1) According to your graphed data is one buffer (beaker 1-3) better or worse than the other(s)? Explain.

(Q2) Write out the chemical reaction that occurs in the Acetic Acid / Acetate buffer when

NaOH is added

HCl is added

(Q3) Write out the chemical reaction that occurs in the Ammonia/Ammonium buffer when

NaOH is added

HCl is added

(Q4) Write out the chemical reaction that occurs in the Distilled water when

NaOH is added

HCl is added

(Q5) Does distilled water make a good buffer? Why or why not?

(Q6) How can you tell if the buffer is working?

(Q7) What happens when you go beyond the buffer capacity? How is buffer capacity indicated on your graph(s)?

You are asked to prepare 3.4L of a HCN/NaCN buffer that has a pH of 9.55 and an osmotic pressure of 1.13atm at 298 K. What masses of HCN and NaCN should you use to prepare the buffer? (Assume complete dissociation of NaCN.)

Hydrogen bromide, HBr, is a colourless gas. Consider its dissociation reaction 2HBr (g) « H2 (g) + Br2 (g) DfHo (kJ/mol) -36.4 +30.9 So (J/K.mol) +198.7 +130.7 +245.5 ooo a) Determine DeltaH , DeltaS , DeltaG , and Kp (all at T= 298 K) for this reaction. b) A 100. mL constant volume reaction vessel is loaded with 0.05 mol HBr and heated to 800 K. Calculate the equilibrium constant for this temperature and the partial pressure of Br2 in the equilibrium mixture. Assume Delta standard H and Delta standard S to be independent of temperature.

Correct Answers:

DHo=103.7 kJ/mol, DSo=-21.2 J/K mol, DGo=110.0 kJ/mol, K=5.25 x 10-20

PBr2= PH2=3.78x x 10-3 atm (PHBr is essentially unchanged).

Please show solution

Standardize the KMnO4 using 0.1M (NH4)2(FE(SO4)26H2O (remember dissolve in H2SO4)

please display your full workings

Calculate the mass concentrations of the following gaseous mixtures enclosed in a room at 2 atmospheres and 50 oC:

(a) Nitrogen (40% by mass), oxygen (40% by mass), and carbon dioxide (20% by mass) in the dry condition.

(b) Nitrogen (40% by mass), oxygen (40% by mass), and carbon dioxide (10% by mass), in the presence of 10% H2O by mass.

(c) Nitrogen (40%), oxygen (40% by mass), and carbon dioxide (5% by mass), in the presence of 15% H2O by mass.

(d) Nitrogen (50% by mass), oxygen (40% by mass), in the presence of 20% H2O by mass.

(e) Sketch a graph showing the relationship between %carbon dioxide on the x-axis, and mass concentration on the y-axis and sketch another plot between %water on the x- axis and mass concentration on the y-axis. Explain your plots by comparing the values in parts (a), (b), (c), and (d) and commenting on these value.

Calculate the pH when 48.0 mL of 0.150 M KOH is mixed with 20.0 mL of 0.300 M HBrO (Ka = 2.5 × 10^-9)

What would happen to the moles of H2(g) you collect if the ZnO layer was present? How about the value of R that you would calculate?
From Gas Boyles Law and Experimental Determination of the Ideal Gas constant

Which of the following solutions would have the highest pOH?

How many grams of solid sodium nitrite should be added to 1.00 L of a 0.226 M nitrous acid solution to prepare a buffer with a pH of 4.305 ?

grams sodium nitrite =  g.

A buffer solution contains 0.259 M NaHSO₃ and 0.459 M Na₂SO₃.

If 0.0149 moles of hydrochloric acid are added to 125 mL of this buffer, what is the pH of the resulting solution ?
(Assume that the volume does not change upon adding hydrochloric acid)

What is the pH?

No pKa was given

Please include work as well!

a). Calculate the molar mass in g/mol of the following compound (ammonium dichromate):

(NH₄)₂Cr₂O₇

b). Calculate the mass, in g, of the following: 0.158 mol IF₅ (iodine pentafluoride)

c). Calculate the amount, in moles, of the following: 25.4 g Pb(C₂H₃O₂)₂ (lead (II) acetate)

Professors Note: Make sure that you give your answer in a clear and well-reasoned manner, providing necessary explanation on how did you come up with it.

d). Calculate the percent by mass of C, H, and O in C₆H₁₂O₆ (glucose )

1. What would be the result of failing to mark the solvent front after developing a TLC plate? Would this affect your ability to calculate component Rf values? Why or why not?

2. What would happen if your origin line was oriented so low on the TLC plate that when it was lowered into the TLC chamber it was positioned below the level of the developing solvent (eluent)?

3. Assuming that the separation of a binary mixture in ideal circumstances (concentrated spotting) would be relatively small (less than 0.5 cm), what would be the result of applying too large a spot of this mixture to the TLC plate? How would it affect your ability to distinguish one component from the other on the plate? How would it affect your Rf values? Draw a sample TLC plate to help illustrate your answer.

4. Unknown compound Q is spotted on a TLC plate that is then developed in cyclohexane. The solvent front is measured at 5.2 cm and the distance traveled by compound Q is measured at 3.4 cm. A sample of acetaminophen is spotted on a TLC plate that is then developed in cyclohexane. The solvent front is measured at 4.15 cm and the distance traveled by acetaminophen is measured at 2.70 cm. What can be determined about the identity of compound Q in light of this data?

5. Describe how TLC could be used to monitor a reaction’s progress (product & byproduct formation) in a research/teaching laboratory.

Calicene, like azulene (Problem 15-17), has an unusually large dipole moment for a hydrocarbon. Explain, using resonance structures.

List 3 possible reasons why a person might not observe a reaction even when the activity series indicates that it should. Please explain carefully. Thank you for your help.

3. You have been given the task of purifying a 60 mL sample of toluene. In order to develop your plan of action, you ask about the impurities likely to be present in the sample. You are told that it contains small amounts of acetone (~10%). a Which technique would you choose for the purification process? Why? (1 point) b. Clearly describe the procedure you would use. (3 points) c. What simple chemical test, performed with the original sample and the purified product, will help you confirm that the acetone impurity has been removed during the purification process? (1 point)