18.2.2 Strengths of Organic Bases

Question 1

Which statement is false?

Answer 1

The conjugate base of a strong acid is a much stronger base than water.

Question 2

All of the following are valid indicators of a solution’s alkalinity except:

Answer 2

polarity of the H–X bond

Question 3

Examine the comparison of two bases below, in which pKb values are given. How much more basic is trimethylamine than pure water?

Answer 3

1 × 10^10 as basic as pure water

Question 4

Using the electronegativity values for the following elements, calculate which compound should be the weakest acid based on electronegativity values alone.

H = 2.1, C = 2.5, N = 3.0, O = 3.5, F = 4.0

Compounds:
methane, ammonia, water, hydrofluoric acid

Answer 4

Methane

Question 5

In comparing three organic nitrogen compounds pictured below, we find that the conjugate acid of the nitrile is the most acidic molecule. Which compound is the strongest base?

Answer 5

The amine

Question 6

Which of the following does not serve as useful information in predicting the relative base strength of a molecule?

Answer 6

Relative acid strength

Question 7

What best explains why oxalic acid (H2C2O4 ) is a stronger acid than citric acid (H3C6H5O7 ), acetic acid (CH3CO2H), or chloroacetic acid (ClCH2CO2H)?

Answer 7

Oxalic acid is most willing to give up a proton because the X group in the X–O–H has strong inductive effects.

Question 8

Calculate the pH, pOH, and [H+] of a hypothetical 2.4 x 10^-3M solution of OH- at 25 degrees C. Recall that water is amphoteric; it undergoes autoionization as described by this reaction: 2H2O(l) H3O+(aq) + OH- , this reaction has the equilibrium expression: Kw = [H3O+][OH-] = [H+][OH-]. In which Kw is called the dissociation constant for water. At 25 degrees C, [H+] = [OH-] = 1.0 x10^-7 M, and Kw = 1.0 x 10^-14 mol2/L2. The units for Kw are customarily left out, so that Kw = 1.0 x 10^-14.

Answer 8

pH = 11.38
pOH = 2.62
[H + ] = 4.17 × 10−12 M

Question 9

Which of the following strong bases is not likely to be used as a laboratory reagent?

Answer 9

LiOH

Question 10

Which statement is false?

Answer 10

In bases of the form X–O–H, X is highly electronegative.