Chemistry, 22.04.2020 18:13 mbonilla073

You determine that it takes 26.0 mL of base to neutralize a sample of your unknown acid solution. The pH of the solution was 7.82 when exactly 13 mL of base had been added. What is the pKa of your unknown acid?

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Answer from: Jrstx333

Complete Question

You determine that it takes 26.0 mL of base to neutralize a sample of your unknown acid solution. The pH of the solution was 7.82 when exactly 13 mL of base had been added, you notice that the concentration of the unknown acid was 0.1 M. What is the pKa of your unknown acid?

The pK_a value is pK_a =7.82

Explanation:

From the question we are told

The volume of base is V_B = 26.mL = 0.0260L

The pH of solution is pH = 7.82

The concentration of the acid is C_A = 0.1M

From the pH we can see that the titration is between a strong base and a weak acid

Let assume that the the volume of acid is V_A = 18mL= 0.018L

Generally the concentration of base

$C_B = \frac{C_AV_A}{C_B}$

Substituting value

$C_B = \frac{0.1 * 0.01800}{0.0260}$

C_B= 0.0692M

When 13mL of the base is added a buffer is formed

The chemical equation of the reaction is

$HA_{(aq)} + OH^-_{(aq)} -------- A^{+}_{(aq)} + H_2 O_{(l)}$

Now before the reaction the number of mole of base is

$No \ of \ moles[N_B] = C_B * V_B$

Substituting value

N_B = 0.01300 * 0.0692

$= 0.0009 \ moles$

Now before the reaction the number of mole of acid is

$No \ of \ moles = C_B * V_B$

Substituting value

N_A = 0.01800 *0.1

$= 0.001800 \ moles$

Now after the reaction the number of moles of base is zero i.e has been used up

this mathematically represented as

N_B ' = N_B - N_B = 0

The number of moles of acid is

N_A ' = N_A - N_B

$= 0.0009\ moles$

The pH of this reaction can be mathematically represented as

$pH = pK_a + log \frac{[base]}{[acid]}$

Substituting values

$7.82 = pK_a +log \frac{0.0009}{0.0009}$

pK_a =7.82

Answer from: Quest

explanation:

i think option no d is the correct answer

40 points and brainliest to anyone who can answer these

Answer from: Quest

solute : a solute is a substance that is dissolved in another substance is known as a solvent. it is mixed with a special mixture know as homogeneous mixture.

solvent: a solvent is a substance that dissolved a solute, which results in a solution is known as solvent.

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