Chapter 8: Acids and bases

Carbonic acid, H2CO3 , is a polyprotic acid. How many protons can it donate?

2 protons

In a neutralization reaction, how many mol of HCl are needed to react with 4 mol of NaOH?

4 mol HCL

What is a neutralization reaction?

A neutralization reaction is one in which an acid and a base react to produce water and a salt (a "neutral" solution).

What are the products of a neutralization reaction?

A neutralization reaction produces a salt and water.

Explain how the molar concentration of carbonic acid in the blood would be changed during a situation of acidosis.

A situation of high blood CO2 levels and low pH is termed acidosis. A high concentration of CO2 is a stress on the left side of the equilibrium. The equilibrium will shift to the right in an effort to decrease the concentration of CO2 . This will cause the molar concentration of carbonic acid (H2CO3 ) to increase.

Explain how the molar concentration of carbonic acid in the blood would be changed during a situation of alkalosis.

A situation of low blood CO2 levels and high pH is termed alkalosis. A low concentration of CO2 is a stress on the left side of the equilibrium. The equilibrium will shift to the left in an effort to increase the concentration of CO2. This will cause the molar concentration of carbonic acid (H2CO3) to decrease.

Describe the purpose of a titration

A titration is a commonly used method for chemical analysis. A base of unknown concentration is titrated with a solution of standard acid. The concentration of the base can be calculated from the molarity and volume of the standard solution and the volume of the unknown base solution. Conversely, the concentration of an unknown acid can be determined by titration with standard base.

What function does an indicator perform?

An indicator is a substance that is added to a solution and changes color as the solution reaches a certain pH. It is often used in the technique of titration to determine the equivalence point.

Distinguish between the terms acid-base strength and acid-base concentration

Concentration refers to the quantity of acid or base contained in a specified volume of solvent. Strength refers to the degree of dissociation of the acid or base

Consider two beakers, one containing a mixture of HCl and NaCl (each solute is 0.10 M) and the other containing a mixture of CH3COOH and CH3COONa (each solute is also 0.10 M). If we add 0.10 M NaOH (10.0 mL) to each beaker, which solution will have the greater change in pH? Why?

HCl/NaCl is not a buffer solution. It is a strong acid and a salt. The NaOH would produce a significant pH change. On the other hand, CH3COOH/CH3COONa is a buffer solution because it is a weak acid and its salt. Therefore, it would resist significant pH change upon addition of a strong base.

Write an equation to represent the neutralization of an aqueous solution of HNO3 with an aqueous solution of NaOH

HNO3 (aq) 1 NaOH(aq )→ H2O(l) 1 NaNO3 (aq)

Consider two beakers, one containing 0.10 M NaOH and the other, 0.10 M NH3 . Which solution has the greater pH? Why?

NaOH is a strong base; consequently [NaOH] = [OH-]. For NaOH, [OH-] is therefore equal to 1.0 x 10-1M and [H3O+] is equal to 1.0 x 10-13M. NH3 is a weak base; consequently, [NH3] > [OH-]. For NH3, [OH-] is less than 1.0 x 10-1M and [H3O+] is greater than 1.0 x 10-13M. Because pH = -log[H3O+], the solution of NaOH has a greater pH than the solution of NH3. When comparing a strong base with a weak base, the weaker base (with the same concentration) will have a lower pH.

Consider two beakers, one containing a mixture of NaOH and NaCl (each solute is 0.10 M) and the other containing a mixture of NH3 and NH4Cl (each solute is also 0.10 M). If we add 0.10 M HNO3 (10.0 mL) to each beaker, which solution will have the greater change in pH? Why?

NaOH/NaCl is not a buffer solution. It is a strong base and a salt. The HNO3 would produce a significant pH change. On the other hand, NH3/NH4Cl is a buffer system. It is a weak base and its salt. It would resist significant pH change upon addition of strong acid.

In a neutralization reaction, how many mol of NaOH are needed to react with 3 mol of HCl?

Neutralization reactions require equal numbers of moles of H3O+ and OH-. Therefore, 3 mol of NaOH are needed to react with 3 mol of HCl.

What are the essential differences between the Arrhenius and Brønsted-Lowry theories?

The Brønsted-Lowry theory provides a broader view of acidbase theory than does the Arrhenius theory. Brønsted-Lowry emphasizes the role of the solvent in the dissociation process.

Consider two beakers, one containing 0.10 M HCl and the other, 0.10 M CH3COOH. Which solution has the greater pH? Why?

The beaker containing 0.10 M CH3COOH. CH3COOH is a weaker acid than HCl. Thus, it has a higher pH than HCl

Criticize the following statement: A lakewater sample of pH = 3.0 is twice as acidic as a lakewater sample of pH = 6.0.

The statement is incorrect. The pH = 3 solution is 1000 times as acidic as the pH = 6 solution because pH is a logarithmic function.

Can a dilute solution of a strong acid ever have a higher pH than a more concentrated solution of a weak acid? Why or why not

Yes, both strength and concentration determine pH.

a. Define an acid according to the Arrhenius theory. b. Define an acid according to the Brønsted-Lowry theory

a. An Arrhenius acid is a substance that dissociates, producing hydrogen ions. b. A Brønsted-Lowry acid is a substance that behaves as a proton donor

Classify each of the following as either a Brønsted-Lowry acid, base, or as amphiprotic. a. H3O+ b. OH- c. H2O

a. Brønsted-Lowry acid b. Brønsted-Lowry base c. amphiprotic

Classify each of the following as either a Brønsted-Lowry acid, base, or as amphiprotic. a. NH4 + b. NH3 c. CH3CH2CH2NH3 +

a. NH4+ is a Brønsted-Lowry acid .b. NH3 is a Brønsted-Lowry base. c. CH3CH2CH2NH3+ is a Brønsted-Lowry acid.

a. Define a base according to the Arrhenius theory. b. Define a base according to the Brønsted-Lowry theory

a.An Arrhenius base is a substance that dissociates, producing hydroxide ions. b. A Brønsted-Lowry base is a substance that behaves as a proton acceptor.

Why is ammonia described as a Brønsted-Lowry base and not an Arrhenius base?

mmonia is not described as an Arrhenius base because it cannot dissociate to produce an OH-. However, it can act as a proton acceptor, or Brønsted-Lowry base:NH3(aq) + H2O(l) NH4+(aq) + OH-(aq)