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Organic chemistry problems

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1.What is the change in pH when 0.005 moles of HCl is added to 0.100 L of a buffer solution that is 0.100 M in CH3CO2H and 0.100 M NaCH3CO2? The Ka for acetic acid is 1.8 x 10 -5.

2. What is the resulting pH when 0.005 moles of KOH is added to 0.100 L of a buffer solution that is 0.100 M in H2PO4- and 0.100 M HPO4 2- and the Ka2= 6.2 x 10 -8.

3. Calculate the molar solubility of thallium chloride in 0.20M NaCl at 25 degrees Celcius. Ksp for TICl is 1.7 x 10 -4.

4. What volume of 0.500 M HNO3 is needed to titrate 60.00 mL of 0.500 M Ca(OH)2 to the equivalence point?

5. What is the chromium ion concentration for a saturated solution of Cr(OH)3 if the Ksp for Cr(OH)3 is 6.7 x 10 -31?

6. What is the molar solubility of Mg(OH)2 in a basic solution with a pH of 12.00? Ksp for Mg(OH)2 is 5.6 x 10-12.

7. What is the pH of a solution made by mixing 15.00mL of 0.10M acetic acid with 15.00mL of 0.10 M KOH? Assume that the volumes of the solutions are additive. Ka=1.8 x 10-5 for CH3CO2H.

8. Formic acid (HCO2H, Ka=1.8 x 10 raised to the -4) is the principal component in the venom of stinging ants. What is the molarity of a formic acid solution if 25.00mL of the formic acid solution requires 49.80mL of 0.0567 M NaOH to reach the equivalence point?

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1. What is the change in pH when 0.005 moles of HCl is added to 0.100 L of a buffer solution that is 0.100 M in CH3CO2H and 0.100 M NaCH3CO2? The Ka for acetic acid is 1.8 x 10 -5.

A buffer solution is one in which the pH of the solution is "resistant" to small additions of either a strong acid or strong base. Buffers usually consist of a weak acid and its conjugate base, in relatively equal and "large" quantities. Calculations are based on the equation for the ionization of the weak acid in water forming the hydronium ion and the conjugate base of the acid. "HA" represents any weak acid and "A-" represents the conjugate base.

HA(aq) + H2O(l) --> H3O+(aq) + A-(aq)

When a strong acid is added to a buffer solution the conjugate base present in the buffer consumes the hydronium ion converting it into water and the weak acid of the conjugate base.

A-(aq) + HCl+(aq) --> H2O(l) + HA(aq)

So your first step is to write the equation for the ionization of acetic acid in water and the related Ka expression rearranged to solve for the hydronium ion concentration.
CH3COOH(aq) + H2O(l) --> H3O+(aq) + CH3COO-(aq)
[H3O+] = Ka[CH3COOH][CH3COO-]

Next, make and ICE chart, which I have attached. Let "x" represent the hydronium ion concentration once equilibrium has been re-established. We will assume that all of the added acid is consumed.

Thirdly, substitute into the Ka expression and solve for the hydronium ion concentration. Convert ...

Solution Summary

Organic chemistry problems involving buffers, pH calculations, and equivalence points.

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Assorted Organic, Bio-Organic Chemistry Problems

Please see the attached file for the complete problems.

1) Label each pair of stereoisomers below as:
a) enantiomers b) diastereomers c) identical

2) Convert the following Fischer projections into a tetrahedral representation, and assign R or S stereochemistry to each.

3) The reaction below is an example of:

a. nucleophilic addition
b. electrophilic addition
c. nucleophilic acyl substitution
d. electrophilic subsitition

4) Refer to the data below to answer the following questions:

Amino Acid Isoelectric point
Arginine 10.76
Glutamic Acid 3.22
Tryptophan 5.89

The most basic amino acid is ____
The most acidic amino acid is ___

5) MATCH a structure from the list below to each of the following terms. Place the letter of the structure in the blank to the left of the term which it describes.

___ an octapeptide
___ an amino acid in its zwitterionic form
___ a polypeptide which gives four fragments on treatment with chymotrypsin
___ a carboxyl-protected amino acid
___ a peptide coupling reagent
___ small organic molecules which act as coenzymes

6) MATCH each of the following terms to a structure from the list below. There is only one correct structure for each term, and structures may be used more than once. Place the letter of the structure in the blank to the left of the corresponding term.

_________ a phosphoglyceride
_________ monoterpene precursor
_________ a triglyceride
_________ a sphingolipid
_________ a soap
_________ a steroid
_________ a sesquiterpene

8) Choose a structure from the list provided below that best fits each of the following descriptions. Place the letter of the structure in the blank to the left of the description. There is only one correct answer for each question.

a. starch
b. cellulose
c.

d.

e.

f. sucrose

___ a monosaccharide that give a negative benedict's test
___ -D-glucopyranose in a Haworth projection
___ a disaccharide

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