Question

8. Calculate the hydrogen ion concentration of the weak acid in
each of the following solutions. Note that the ionization constants
may be such that the change in electrolyte concentration cannot be
neglected and the quadratic formula or successive approximations
may be required.

(a) 0.0184 M HCNO ( Ka = 3.46 x 10 - 4 ) (b) 0.02173 M CH2 ClCO2 H
( Ka = 1.4 x 10 -3 )

Answer #1

A.

Step 1. Write the dissociation equation.

Step 2. Take reaction to equilibrium.

HCNO | CNO - | H+ | |

initial | 0.0184 M | 0 | 0 |

change | - x | + x | + x |

equilibrium | 0.0184 - x | x | x |

Step 3. Write the dissociation constant.

Step 4. Add the known values to the latter equation.

Step 5. Solve for x = [H^{+}].

B.

Step 1. Write the dissociation equation.

Step 2. Take reaction to equilibrium.

ClCOOH | ClCOO - | H+ | |

initial | 0.02173 M | 0 | 0 |

change | - x | + x | + x |

equilibrium | 0.02173 - x | x | x |

Step 3. Write the dissociation constant.

Step 4. Add the known values to the latter equation.

Step 5. Solve for x = [H^{+}].

1. Calculate the hydrogen ion concentration, [H+ ],
for the two weak acids (pH=-log[H+ ], or [H+
]=antilog (-pH). If you have difficulty finding or using the
antilog function on your calculator, simply use this:
[H+ ]=10-pH .
2. Calculate the hydroxide ion concentration, [OH- ],
for the weak base using this formula: pOH=14-pH, then
[OH- ]=antilog (-pOH) or
[OH-]=10-pOH.
3. Calculate the molar concentrations of the vinegar as well as
ammonia. Both are industry standard 5.00% by mass solutions...

Determine the pH of each of the following
solutions.
(a) 0.821 M hydrogen peroxide (weak acid with Ka
= 2.4e-12).
(b) 0.306 M boric acid (weak acid with Ka =
5.8e-10).
(c) 0.309 M pyridine (weak base with Kb =
1.7e-09).

Calculate pH of 0.10 M hydrochloric acid (why no Ka?)
Calculate the pH of a 0.100 M calcium hydroxide (hint: write the
formula first & rxn in water)
Calculate the pH and % ionization of a 0.05 M hydrofluoric acid
(ka = 8.0 x 10 -4) .
What is the hydrogen ion concentration for a hydrochloric acid
solution that has a pH of 2.30?

Calculate the molar hydronium ion concentration in a solution
containing 0.23M hypochlorus acid (HOCl), a monoprotic weak acid
used in bleach solutions. For HOCl, Ka=2.9x10^-8

Determine the pH of each of the following solutions.
(a) 0.123 M propionic acid (weak acid with Ka = 1.3e-05).
(b) 0.378 M hypoiodous acid (weak acid with Ka = 2.3e-11).
(c) 0.688 M pyridine (weak base with Kb = 1.7e-09).

Cyanic acid, HCNO, is a weak acid with the following
equilibrium:
HCNO(aq) + H2O(l) ⇌
CNO-(aq) +
H3O+(aq)
In a 0.200 M aqueous solution of HCNO, the concentration of
H3O+ is 6.50 x 10-3M.
The equilibrium constant (Kc) for this reaction
is

Cyanic acid, HCNO, is a weak acid with the following
equilibrium: HCNO(aq) + H2O(l) ⇌ CNO-(aq) +
H3O+(aq) In a 0.200 M aqueous solution of
HCNO, the concentration of H3O+ is 6.50 x
10-3M. The equilibrium constant (Kc) for this reaction
is?

QUESTION 1: What is the pH of an aqueous solution with a
hydrogen ion concentration of [H ] = 5.6 × 10–5 M?
QUESTION 2: Complete this table pf values for thre aqueous
solutions at 25C.
[H]+ [OH-] ph
Solution A 7.7*10^-6 M X X
Solution B X 0.097 X
Solution C X X 8.84

A certain weak acid, HA, has a Ka value of 1.4×10−7.
1.Calculate the percent ionization of HA in a 0.10 M
solution.
2.Calculate the percent ionization of HA in a 0.010 M
solution.

Using the ionization constants for acetic acid (Ka= 1.8 x 10^-5)
and ammonia (Kb= 1.8 x10^-5), calculate the expected pH of the
above four solutions (0.100 M sodium acetate,
ammonium chloride, acetic acid and ammonia). Use the simplified
version instead of the quadratic equation.

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