Concept explainers
(a)
Interpretation:
The molarity of the hydrofluoric acid in the solution is to be calculated.
Concept Introduction:
The molarity of a solution is defined as number of moles of solute in 1L of solution. This is mathematically represented as follows:
Here, n is number of moles and v is volume of solution.
The pressure, volume, moles and temperature of a gas are related to each other according to an equation,
Here, p is pressure, v is volume, n is number of moles, r is gas constant and t is temperature of the gas.

Answer to Problem 105P
Thus, the molarity of the HF solution is 0.02498 M.
Explanation of Solution
The pressure, volume, moles and temperature of a gas are related to each other according to an equation,
Here,
Putting the given values in the ideal gas equation, we get.
Thus, the number of moles of HF = 0.02498 mol.
Now, the molarity of this solution is to be calculated.
Thus, the molarity of the HF solution is 0.02498 M.
(b)
Interpretation:
The acid ionization constant,
Concept Introduction:
Weak acids do not dissociate completely. Let HA be a weak acid. The dissociation of the weak acid can be represented by the chemical equation,
The equation for acid dissociation constant can be written from this chemical equation.

Answer to Problem 105P
The acid dissociation constant of hydrofluoric acid is
Explanation of Solution
Hydrofluoric acid is a weak acid. Hence, it does not dissociate completely. The dissociation of the given weak acid can be represented by the chemical equation,
The equation for acid dissociation constant can be written from this chemical equation.
The concentrations of each of the ions at equilibrium can be obtained from the ICE table, where ICE represents the Initial, Change and Equilibrium concentrations of the weak acid.
The hydrogen ion concentration can be obtained from the given pH. The pH is defined as the negative logarithm of the hydrogen ion concentration.
The pH of the weak acid solution at equilibrium is 1.88. Thus, we can calculate the concentration of the hydrogen ion.
We calculated the “x” which is the concentration of hydrogen ion. The concentration of the anion is also “x”. Thus,
Now, we need to calculate the concentration of
Thus, the concentration of hydrofluoric acid is
The concentrations of the anion, hydrogen ion and hydrofluoric acid are used in the equation used for acid dissociation constant.
Thus, the acid dissociation constant of hydrofluoric acid is
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Chapter 8 Solutions
EP INTRO.TO GENERAL,ORGANIC...-OWL ACCE
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