Answer:
a. 1.78x10⁻³ = Ka
2.75 = pKa
b. It is irrelevant.
Explanation:
a. The neutralization of a weak acid, HA, with a base can help to find Ka of the acid.
Equilibrium is:
HA ⇄ H⁺ + A⁻
And Ka is defined as:
Ka = [H⁺] [A⁻] / [HA]
The HA reacts with the base, XOH, thus:
HA + XOH → H₂O + A⁻ + X⁺
As you require 26.0mL of the base to consume all HA, if you add 13mL, the moles of HA will be the half of the initial moles and, the other half, will be A⁻
That means:
[HA] = [A⁻]
It is possible to obtain pKa from H-H equation (Equation used to find pH of a buffer), thus:
pH = pKa + log₁₀ [A⁻] / [HA]
Replacing:
2.75 = pKa + log₁₀ [A⁻] / [HA]
As [HA] = [A⁻]
2.75 = pKa + log₁₀ 1
<h3>2.75 = pKa</h3>
Knowing pKa = -log Ka
2.75 = -log Ka
10^-2.75 = Ka
<h3>1.78x10⁻³ = Ka</h3>
b. As you can see, the initial concentration of the acid was not necessary. The only thing you must know is that in the half of the titration, [HA] = [A⁻]. Thus, the initial concentration of the acid doesn't affect the initial calculation.
Refer to the diagram shown below.
The second axis is at the centroid of the rod.
The length of the rod is L = 100 cm = 1 m
The first axis is located at 20 cm = 0.2 m from the centroid.
Let m = the mass of the rod.
The moment of inertia about the centroid (the 2nd axis) is
According to the parallel axis theorem, the moment of inertia about the first axis is
The ratio of the moment of inertia through the 2nd axis (centroid) to that through the 1st axis is
Answer: 0.676
The volume (in cm³) gained by a person who gains 11.8 lb of fat is 5830.49 cm³
<h3>What is density? </h3>
The density of a substance is simply defined as the mass of the subtance per unit volume of the substance. Mathematically, it can be expressed as
Density = mass / volume
<h3>How to convert pounds to grams </h3>
1 lb = 453.592 g
Therefore,
11.8 lb = 11.8 × 453.592
11.8 lb = 5352.3856 g
<h3>How to determine the volume </h3>
- Mass = 5352.3856 g
- Density = 0.918 g/cm³
- Volume =?
Volume = mass / density
Volume = 5352.3856 / 0.918
Volume = 5830.49 cm³
Learn more about density:
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Answer is: household ammonia has 10 times higher H⁺ concentration.
1) pH(household ammonia) = 11.5.
pH = -log[H⁺], approximately the negative of the base 10 logarithm of the molar concentration of hydrogen ions.
[H⁺] = 10∧(-pH).
[H⁺] = 10∧(-11.5).
[H⁺] = 3.16·10⁻¹² M; concentration of hydrogen ions.
2) pH(household bleach) = 12.5.
[H⁺] = 10∧(-12.5).
[H⁺] = 3.16·10⁻¹³ M.
3) 3.16·10⁻¹² M / 3.16·10⁻¹³ M = 10.
