Phosphate ions are abundant in cells, both as the ions themselves and as important substituents on organic molecules. Most importantly, the pKa for the H2PO4 ion is 7.20, which is very close to the normal pH in the body. H2PO4(aq) + H2O() H3O+(aq) + HPO42(aq) 1. What should the ratio [HPO42]/[H2PO4] be to control the pH at 7.40?

Complete each of these reactions by filling in the blanks. Predict whether each reaction is product-favored or reactant-favored, and explain your reasoning. (a) _________ (aq) + Br(aq) NH3(aq) + HBr(aq) (b) CH3COOH(aq) + CN(aq) ________ (aq) + HCN(aq) (c) ________ (aq)+H2O () NH3(aq) + OH(aq)

The hydrogen phthalate ion, C8HsO4, is a weak acid with Ka = 3.91 106. C8H5O4(aq)+H2O(l)C8H4O42(aq)+H3O+(aq) What is the pH of a 0.050 M solution of potassium hydrogen phthalate. KC8H5O4? Note: To find the pH for a solution of the anion, we must take into account that the ion is amphiprotic. It can be shown that, for most cases of amphiprotic ions, the H3O+ concentration is [H3O+]=Ka1Ka2 For phthalic acid, C8H6O4 is Ka1 is 1.12 103, and Ka2 is 3.91 106.

Most naturally occurring acids are weak acids. Lactic acid is one example. CH3CH(OH)CO2H(s)+H2O(l)H3O+(aq)+CH3CH(OH)CO2(aq) If you place some lactic acid in water, it will ionize to a small extent, and an equilibrium will be established. Suggest some experiments to prow that this is a weak acid and that the establishment of equilibrium is a reversible process.

Write the chemical equation and the expression for the equilibrium constant, and calculate Kb for the reaction of each of the following ions as a base. (a) sulfate ion (b) citrate ion

Write chemical equations showing the individual proton-transfer steps that occur in aqueous solution for each of the following acids. a. H2C2O4 (oxalic acid) b. H2C4H4O6 (tartaric acid)

For conjugate acidbase pairs, how are Ka and Kb related? Consider the reaction of acetic acid in water CH3CO2H(aq)+H2O(l)CH3CO2(aq)+H3O+(aq) where Ka = 1.8 105 a. Which two bases are competing for the proton? b. Which is the stronger base? c. In light of your answer to part b. why do we classify the acetate ion (CH3CO2) as a weak base? Use an appropriate reaction to justify your answer. In general, as base strength increases, conjugate acid strength decreases. Explain why the conjugate acid of the weak base NH3 is a weak acid. To summarize, the conjugate base of a weak acid is a weak base and the conjugate acid of a weak base is a weak acid (weak gives you weak). Assuming Ka for a monoprotic strong acid is 1 106, calculate Kb for the conjugate base of this strong acid. Why do conjugate bases of strong acids have no basic properties in water? List the conjugate bases of the six common strong acids. To tie it all together, some instructors have students think of Li+, K+, Rb+, Cs+, Ca2+, Sr2+, and Ba2+ as the conjugate acids of the strong bases LiOH, KOH. RbOH, CsOH, Ca(OH)2, Sr(OH)2, and Ba(OH)2. Although not technically correct, the conjugate acid strength of these cations is similar to the conjugate base strength of the strong acids. That is, these cations have no acidic properties in water; similarly, the conjugate bases of strong acids have no basic properties (strong gives you worthless). Fill in the blanks with the correct response. The conjugate base of a weak acid is a_____base. The conjugate acid of a weak base is a_____acid. The conjugate base of a strong acid is a_____base. The conjugate acid of a strong base is a_____ acid. (Hint: Weak gives you weak and strong gives you worthless.)

Boron trifluoride, BF3, and ammonia, NH3, react to produce BF3: NH3. A coordinate covalent bond is formed between the boron atom on BF3 and the nitrogen atom on NH3. Write the equation for this reaction, using Lewis electron-dot formulas. Label the Lewis acid and the Lewis base. Determine how many grams of BF3: NH3 are formed when 10.0 g BF3 and 10.0 g NH3 are placed in a reaction vessel, assuming that the reaction goes to completion.

Consider the following ions: NH4+, CO32, Br, S2, and ClO4. (a) Which of these ions in water gives an acidic solution and which gives a basic solution? (b) Which of these anions will have no effect on the pH of an aqueous solution? (c) Which ion is the strong base? (d) Write a chemical equation for the reaction of each basic anion with water.