Chemistry, 07.10.2019 17:30 justachelseafan

Weak acids and bases are those that do not completely dissociate in water. the dissociation of the acid or base is an equilibrium process and has a corresponding equilibrium constant. ka is the equilibrium constant for the dissociation of a weak acid and kb is the equilibrium constant for the dissociation of a weak base. what is the ph of a solution that has 0.125 m ch3cooh and 0.125 m h3bo3? ka of ch3cooh = 1.8 × 10−5 and ka of h3bo3 = 5.4 × 10−10 answer unselected 4.74 unselected 5.64 unselected 2.82 unselected 2.52 unselected

Answers: 2

Show answers

Answers

Answer from: candigirl8847

pH=2.82

Explanation:

pH is a scale used to indicate if a water-based solution is acidic or basic, and is defined by the following equation:

$pH=- log (H^{+})$ Equation (1)

In aqueous solutions there are no ions $H^{+}$ , because the proton is transferred to $H_{2}O$ to form hydronium ions, $H_{3}O^{+}$ . Thus, we can determine the pH of the solution, finding the molar concentration of $H_{3}O^{+}$ ions:

$[pH=- log (H_{3}O^{+})$ Equation (2)

The solution prepared contains two weak acids, each one undergoes an equilibrium process with the corresponding equilibrium constant Ka, as it is represented in the following reaction for a weak acid HA:

HA + $H_{2}O$ ⇔ $H_{3}O^{+}$ + $A^{-}$

The equilibrium constant is defined by the equilibrium concentration of products over reactants:

$k= \frac{[H_3O^{+}][A^{-}]}{[HA][H_2O]}$ Equation (3)

However, the molar concentration of water is essentially constant for reactions in aqueous solutions, then the acid dissociation constant is defined as follow:

$k_a=K[H_2O]= \frac{[H_3O^{+}][A^{-}]}{[HA]}$ Equation (4)

Information for CH_3COOH :

Reaction: CH_3COOH + $H_{2}O$ ⇔ $H_{3}O^{+}$ + $CH_3COO^{-}$

Initial moles per Liter: 0.125 M + A ⇔ 0 + 0

Reacting moles per liter: -x + -x ⇔ x + x

Equilibrium mole per liter: 0.125 M-x+ A-x ⇔ x + x

$k_a= 1.8*10^{-5}$

Information for H_3BO_3 :

Reaction: H_3BO_3 + $H_{2}O$ ⇔ $H_{3}O^{+}$ + $H_2BO_3^{-}$

Initial moles per Liter: 0.125 M + A ⇔ 0 + 0

Reacting moles per liter: -y + -y ⇔ y + y

Equilibrium mole per liter: 0.125 M-y+ A-y ⇔ y + y

$k_a= 5.4*10^{-10}$

Replacing the equilibrium information of each acid in equation 4, we get:

For CH_3COOH :

$1.8*10^{-5} =\frac{[x][x]}{[0.125-x]}$ Equation (5)

For H_3BO_3 :

$5.4*10^{-10} =\frac{[y][y]}{[0.125-y]}$ Equation (6)

Solving equation 5 and 6:

For CH_3COOH :

$x = [H_{3}O^{+}] = 1.49*10^{-3}$

For H_3BO_3 :

$y = [H_{3}O^{+}] = 1.64*10^{-6}$

Due to both acids are in the same solution, the total concentration of $[H_{3}O^{+}]$ is (x+y) $1.5064*10^{-3}$ . Replacing this concentration in equation 2, we get:

$pH= -log (1.5064*10^{-3})=2.82$

Answer from: Quest

It d from what i know

Answer from: Quest

it takes on an electronical energy

Other questions on the subject: Chemistry

Chemistry, 21.06.2019 22:00, pettygirl13

Describe the particles of all three phases of matter in the root beer float. (how are the particles arranged and moving? )

Answers: 3

continue

Chemistry, 22.06.2019 05:30, jameskarbar9p8c9d2

Match the following vocabulary terms to their definitions. 1. amount of energy required to change 1 gram of material from the solid to the liquid state at its melting point 2. a measure of the kinetic energy of the particles of a substance 3. the amount of heat energy required to raise the temperature of 1 gram of liquid water from 14.5°c to 15.5°c 4. amount of energy required to change 1 gram of material from the liquid to the gaseous state at its boiling point 5. the amount of energy required to change 1 gram of a substance 1°c a. temperature b. latent heat of vaporization c. latent heat of fusion d. calorie e. specific heat

Answers: 1

continue

Chemistry, 22.06.2019 12:30, pup88

According to the valence shell electron pair repulsion (vsepr) theory, a molecule that has four electron groups around the central atom will exhibit what electron geometry? view available hint(s) according to the valence shell electron pair repulsion (vsepr) theory, a molecule that has four electron groups around the central atom will exhibit what electron geometry? trigonal bipyramidal tetrahedral square planar determination of electron geometry requires information on whether the electron groups are lone pairs or bonding groups.

Answers: 2

continue

Chemistry, 22.06.2019 14:30, larey

How many molecules are in 6.0 moles of methane

Answers: 1

continue

You know the right answer?

Weak acids and bases are those that do not completely dissociate in water. the dissociation of the a...