Like all equilibrium constants, the value of K_w depends on temperature. At body temperature (37 °C), K_w = 2.4×10^–14. What are the [H₃O⁺] and pH of pure water at body temperature?

Problema 54

The value of K_w increases with increasing temperature. Is the autoionization of water endothermic or exothermic?

Problema 55

Calculate the pH of each acid solution. Explain how the resulting pH values demonstrate that the pH of an acid solution should carry as many digits to the right of the decimal place as the number of significant figures in the concentration of the solution. [H₃O⁺] = 0.044 M [H₃O⁺] = 0.045 M [H₃O⁺] = 0.046 M

Problema 56

Determine the concentration of H₃O⁺ to the correct number of significant figures in a solution with each pH. Describe how these calculations show the relationship between the number of digits to the right of the decimal place in pH and the number of significant figures in concentration. pH = 2.50 pH = 2.51 pH = 2.52

Problema 57a

For each strong acid solution, determine [H₃O⁺], [OH^–], and pH. a. 0.25 M HCl

Problema 57b

For each strong acid solution, determine [H₃O⁺], [OH^–], and pH. b. 0.015 M HNO₃

Problema 57c

For each strong acid solution, determine [H₃O⁺], [OH^–], and pH. c. a solution that is 0.052 M in HBr and 0.020 M in HNO₃

Problema 57d

For each strong acid solution, determine [H₃O⁺], [OH^–], and pH. d. a solution that is 0.655% HNO₃ by mass (assume a density of 1.01 g/mL for the solution)

Problema 58

Determine the pH of each solution. a. 0.048 M HI b. 0.0895 M HClO₄ c. a solution that is 0.045 M in HClO₄ and 0.048 M in HCl d. a solution that is 1.09% HCl by mass (assume a density of 1.01 g/mL for the solution)

Problema 59

What mass of HI must be present in 0.250 L of solution to obtain a solution with each pH value?

a. pH = 1.25 b. pH = 1.75 c. pH = 2.85

Problema 60

What mass of HClO₄ must be present in 0.500 L of solution to obtain a solution with each pH value? a. pH = 2.50 b. pH = 1.50 c. pH = 0.50

Problema 61

What is the pH of a solution in which 224 mL of HCl(g), measured at 27.2 °C and 1.02 atm, is dissolved in 1.5 L of aqueous solution?

Problema 62

What volume of a concentrated HCl solution, which is 36.0% HCl by mass and has a density of 1.179 g/mL, should be used to make 5.00 L of an HCl solution with a pH of 1.8?

Problema 63

Determine the [H₃O⁺] and pH of a 0.100 M solution of benzoic acid.

Problema 64

Determine the [H₃O⁺] and pH of a 0.200 M solution of formic acid.

Problema 65

Determine the pH of an HNO₂ solution of each concentration. In which cases can you not make the simplifying assumption that x is small? a. 0.500 M b. 0.100 M c. 0.0100 M

Problema 66

Determine the pH of an HF solution of each concentration. In which cases can you not make the simplifying assumption that x is small? (K_a for HF is 6.8×10^–4.) a. 0.250 M b. 0.0500 M c. 0.0250 M

Problema 67

If 15.0 mL of glacial acetic acid (pure HC2H3O2) is diluted to 1.50 L with water, what is the pH of the resulting solution? The density of glacial acetic acid is 1.05 g/mL.

Problema 68

Calculate the pH of a formic acid solution that contains 1.35% formic acid by mass. (Assume a density of 1.01 g/mL for the solution.)

Problema 69

A 0.185 M solution of a weak acid (HA) has a pH of 2.95. Calculate the acid ionization constant (K_a) for the acid.

Problema 71

Determine the percent ionization of a 0.125 M HCN solution.

Problema 72

Determine the percent ionization of a 0.225 M solution of benzoic acid.

Problema 73

What is the percent ionization of an acetic acid solution at the following concentrations? a. 1.00 M b. 0.500 M c. 0.100 M d. 0.0500 M

Problema 74a

Calculate the percent ionization of a formic acid solution having the given concentration. a. 1.00 M