Answer:
pH = 6.76
Explanation:
<em>Ka = 3.4x10⁻⁷; 3.0x10⁻⁵g</em>
<em />
The molarity of the vitamin B1 -Molar mass: 327.268g/mol- solution is:
3.0x10⁻⁵g * (1mol / 327.268g) = 9.167x10⁻⁸M
The Ka expression is:
Ka = <em>3.4x10⁻⁷ = [H⁺] [B1-] / [B1]</em>
<em>Where B1- is the conjugate base of vitamin B1, </em>
In equilibrium, the concentrations are:
[H⁺] = X
[B1-] = X
[B1] = 9.167x10⁻⁸M - X
<em>Where X is reaction coordinate</em>
<em />
Replacing:
3.4x10⁻⁷ = [X] [X] / [9.167x10⁻⁸M - X]
3.117x10⁻¹⁴ -3.4x10⁻⁷X = X²
3.117x10⁻¹⁴ -3.4x10⁻⁷X - X² = 0
Solving for X:
X = -4.15x10⁻⁷M. False solution. There is no negative concentrations.
<h3>X = 7.51x10⁻⁸M</h3><h3 />
That means from the equilibrium of vitamin B1, the [H⁺] = 7.51x10⁻⁸M
From the autoinoization of water:
[H⁺] = 1.0x10⁻⁷M
[H⁺] in the solution is:
1.0x10⁻⁷M + 7.51x10⁻⁸M = 1.751x10⁻⁸M
As pH = -log[H⁺]
<h3>pH = 6.76</h3>