1. Sulfanilic acid (NH2C6H4SO3H) has a pKa of 3.23. How many grams of Na(NH2C6H4SO3) [182.1 g/mol] would you have to dissolve in 125 mL of water to get a pH of 7.97?

a. 0.59

b. 1.2g

c. 3.5g

d. 4.8g

2. When KNO2 is dissolved in water, ___________.

3. Calculate the concentration of HCN in a sol’n prepared by dissolving 10.8 g of NaCN (49 g/mol) in enough water to make 500.0 mL of sol’n.  Ka for HCN = 4.0 x 10-10

1. 		0.0057 M
   		0.0033 M
   		0.41 M
   		0.15 M

4. What is the pH of a sodium formate (68 g/mol) solution prepared by adding 0.680 g of sodium formate to 100.0 mL of water at 25°C? The Ka for formic acid is 1.8 x 10-4 at 25°C.

5. Of the compounds below, a 0.10 M aqueous solution of ________ will have the highest pH.

What is the pH of a solution made by mixing 500 mL of 1.00 M HCN and 1.50 L of 0.250 M NaOH, and then diluting the entire solution to a volume of 3.00 L? (Ka HCN = 4.0 x 10^-10)

• A.

  8.92

• B. 6.52

• C.

  9.88

• D.

  9.27

• E.

  5.08

To obtain one litre of a solution of pH = 7, you should dissolve in water

• A.

  Two mol of HI + two mol of CH₃NH₂

• B.

  One mol of H₂SO₄ + two mol of NH₃

• C.

  One mol of HF + one mole of KOH

• D.

  Two mol of H₂SO₄ + four mol of NaOH

• E.

  Two mol of H₃PO₄ + three mol of Ca(OH)₂

The intermediate product of a chemical process is a chemical paste that is saturated with water. The paste is rolled into a thin layer and placed to dry in a flat area 30m long 15m wide. Drying is enhanced by blowing hot air over the paste, and the mass transfer coefficient is 0.017 m/s. Diffusion of water through the paste is rapid so that the concentration of water vapor at the surface of the paste remains constant at 0.002 gmol/L. Water must be removed from the paste remains at a minimum rate of 9.5 L/min (liquid volume). (Note:MW water=18 and p water=1 g/cm^3.)

a.) What mechanism controls the transfer of water from the paste in the air?

b.) What is the molar rate of water removal that corresponds to a volumetric removal rate of 9.5 L/min?

C.) What is the maximum concentration of water vapor allowable in the air (far from the paste surface) if water must be removed at a rate of at least 9.5 L/min?

D.) Assuming that the mass transfer coefficient remains constant, what can be done to increase the rate of water removal from the paste?

In a

0.57mM

aqueous solution of trimethylacetic acid

C4H9CO2H

, what is the percentage of trimethylacetic acid that is dissociated? You can find some data that is useful for solving this problem in the ALEKS Data resource.

Round your answer to

2

significant digits.

A hot air balloon of 25 m in diameter has a mass of 95 kg including its cage when empty. This balloon is accelerating upward at an acceleration of 1 m/s^2 in the air at a location where the atmospheric pressure and temperature are 85 kPa and 13 C respectively while carrying 3 people with a mass of 70 kg each. Determine the average temperature of the air in the balloon assume equal pressure between the inside of the balloon and its outside.

Determine the molar solubility of AgBr in a solution containing 0.150 M NaBr. K_sp AgBr = 7.7x10^-13

Post-Lab Questions: Answer. 1. What should you examine to determine the precision of your results? Explain. 2. What should you examine to determine the accuracy of your results? Explain. 3. If the standardization of the NaOH in Experiment 7 was not performed correctly and the experimental normality was too low, how would that affect the experimental equivalent weight being determined in this experiment? Would it be too high or too low? Explain. 4. You were allowed to weigh out between 0.35 g and 0.40 g of the unknown sample. If you used 0.35 g for Trial #1 and 0.40 g for Trial #2, would the experimental equivalent weight for Trial 2 be higher, lower or the same as that of Trial #1? Explain. ACID-BASE TITRATION Determination of the equivalent weight of an unknown acid.

4. If I use a catalyst,

a. how will it change the reaction?

b. if it is an equilibrium reaction, how will it change the equilibrium constant?

5. What happens to the equilibrium if I add some of the product to the beaker where the reaction is happening? How does the equilibrium shift? Is it gone forever?

For the diprotic weak acid H2A, Ka1 = 2.2 × 10-6 and Ka2 = 8.4 × 10-9. What is the pH of a 0.0600 M solution of H2A? What are the equilibrium concentrations of H2A and A2– in this solution?

1a)  From the volume of titrant added, calculate the moles of vitamin C for each titration. Show a sample calculation for trial 1, and then just state the final results for the calculation of trials 2 and 3. Use 5 digits in all intermediate values and report the final value to the appropriate number of significant figures.

Trial 1

Trial 2

Trial 3

b) From the results of question 1, calculate the average value for the number of moles of vitamin C titrated. Report the final value to the appropriate number of significant figures.

c) Calculate the precision for the mole values used to calculate the average in question 2.

Data table:

KlO3 concentration= 0.002012 M

Part (a) The cyclopentadienyl anion (C5H5 - ) is commonly used aromatic ligand. The secular equations for describing the interactions of the five unhybridized p orbitals lead to a matrix of the form:

( ?11 − ??11 ?12 − ??12 ?13 − ??13 ?14 − ??14 ?15 − ??15
?21 − ??21 ?22 − ??22 ?23 − ??23 ?24 − ??24 ?25 − ??25
?31 − ??31 ?32 − ??32 ?33 − ??33 ?34 − ??34 ?35 − ??35
?41 − ??41 ?42 − ??42 ?43 − ??43 ?44 − ??44 ?45 − ??45
?51 − ??51 ?52 − ??42 ?53 − ??53 ?54 − ??54 ?55 − ??55)

where ??? is the Hamiltonian integral for orbitals ? and ? and ??? is the overlap integral for orbitals ? and ?. This matrix can be simplified using the approximations of Hückel molecular orbital (MO) theory, which involves two constants ? and ?.

(i) Explain the approximations of Hückel MO theory in terms of ??? and ???, and define ? and ?.

(ii) Re-write the above matrix applying these assumptions. [You may write this matrix (and only the matrix) on paper and copy and paste and image of it into your word document if you wish.] (iii) Briefly explain (without performing any calculations) how this matrix is used to determine the energies and coefficients of the MOs.

How does the absorption capacity of the regenerated activated carbon compare to that original activated carbon? Explain why there is a difference.