Calculate the Ka of a 0.35M weak acid with a pH of 4.2.
1 answer:
Answer:
Ka = 1.14x10⁻⁸
Explanation:
First we <u>calculate [H⁺] from the pH</u>:
- pH = -log[H⁺]
- [H⁺] =
- [H⁺] = 6.31x10⁻⁵ M
For a monoprotic weak acid, the molar concentration of H⁺ of a solution can be expressed as:
- [H⁺] = √(C*Ka)
Where C is the molar concentration of the weak acid solution.
- 6.31x10⁻⁵ M =
- 1.14x10⁻⁸ = Ka
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Answer:
Explanation:
When percentage composition is given, and asked for the empirical formula, it is simplest to assume 100 g of material. Thus,
Mass C = 40.92 g. Moles C = 40.92 g x 1 mole/12 g = 3.41 moles C
Mass H = 4.58 g. Moles H = 4.58 g x 1 mole/1.0 g = 4.58 moles H
Mass O = 54.50 g. Moles O = 54.50 g x 1 mole/16 g = 3.41 moles O
Now, we want to get the moles into whole numbers, so we begin by dividing all by the smallest, i.e. divide all values by 3.41.
Moles C = 3.41/3.41 = 1
Moles H = 4.58/3.41 = 1.34
Moles O = 3.41/3.41 = 1
Now, in order to get 1.34 to be a whole number we multiply it (and all others) by 3
Moles C = 1x3 = 3
Moles H = 1.34x3 = 4
Moles O = 1x3 = 3
Empirical Formula