1) pyridine is a weak base that is used in the manufacture of pesticides and plastic resins. it is also a component of cigarette smoke. pyridine ionizes in water as follows: c5h5n+h2o< -> c5h5nh++oh? the pkb of pyridine is 8.75. what is the ph of a 0.305m solution of pyridine? express the ph numerically to two decimal places. benzoic acid is a weak acid that has antimicrobial properties. its sodium salt, sodium benzoate, is a preservative found in foods, medications, and personal hygiene products. benzoic acid ionizes in water: c6h5cooh< -> c6h5coo? +h+2) the pka of this reaction is 4.2. in a 0.66m solution of benzoic acid, what percentage of the molecules are ionized? express your answer to two significant figures and include the appropriate units.
3 )ammonia, nh3, is a weak base with a kb value of 1.8

1) pH = 9.37

2) α = 0.97%

Explanation:

1) Pyridine is a weak base that ionizes in water as follows:

C₅H₅N(aq) + H₂O(l) ⇄ C₅H₅NH⁺(aq) + OH⁻(aq)

Since pKb is 8.75, we can find the equilibrium constant Kb using the following expression:

pKb = -log Kb

Kb = antilog (-pKb) = antilog (-8.75) = 1.78 × 10⁻⁹

If we know Kb and the initial concentration of the base (Cb) we can find [OH⁻] using the following expression:

[OH⁻] = √(Kb × Cb)

[OH⁻] = √(1.78 × 10⁻⁹ × 0.305) = 2.33 × 10⁻⁵ M

Then, we can find pOH and pH.

pOH = -log [OH⁻]

pOH = -log (2.33 × 10⁻⁵) = 4.63

pH + pOH = 14

pH = 14 - pOH = 14 - 4.63 = 9.37

2) Benzoic acid is a weak acid that ionizes in water as follows:

C₆H₅COOH(aq) ⇄ C₆H₅COO⁻(aq) + H⁺(aq)

Since pKa is 4.2, we can find the equilibrium constant Ka using the following expression:

pKa = -log Ka

Ka = antilog (-pKa) = antilog (-4.2) = 6.3 × 10⁻⁵

If we know Ka and the initial concentration of the acid (Ca) we can find [H⁺] and [C₆H₅COO⁻] using the following expression:

[H⁺] = [C₆H₅COO⁻] = √(Ka × Ca)

[H⁺] = [C₆H₅COO⁻] = √(6.3 × 10⁻⁵ × 0.66) = 6.4 × 10⁻³ M

The percentage of ionized molecules (α) is:

there all right good

explanation:

most historians agree that gabriel mouton, the vicar of st. paul’s church in lyons, france, is the “founding father” of the metric system. he proposed a decimal system of measurement in 1670. mouton based it on the length of one minute of arc of a great circle of the earth (now called a nautical mile, 1852 meters). he also proposed the swing-length of a pendulum with a frequency of one beat per second as the unit of length (about 25 cm). a pendulum beating with this length would have been fairly easy to produce, thus facilitating the widespread distribution of uniform standards. over the years, his work was revised, improved, and extended by a number of french scientists.

the political sponsor of weights and measures reform in the french revolutionary national assembly was the bishop of autun, better known as talleyrand. under his auspices, the french academy appointed several committees to carry out the work of developing a usable system of weights and measures for france. one of the committees recommended a decimalized measurement system based upon a length equal to one ten-millionth of the length of a quadrant of the earth’s meridian (i.e., one ten-millionth of the distance between the equator and the north pole).