7. A student titrated a 15.00-mL sample of a solution containing a weak, monoprotic acid with NaOH. The titration required 17.73 mL of 0.1036 M NaOH to reach the equivalence point. Calculate the concentration (in M) of the weak acid in the sample.

Respuesta :

Answer:  The concentration of the weak acid in the sample is 0.1224 M

Explanation:

The balanced chemical reaction is :

[tex]HA+NaOH\rightarrow NaA+H_2O[/tex]

To calculate the volume of acid, we use the equation given by neutralization reaction:

[tex]n_1M_1V_1=n_2M_2V_2[/tex]

where,

[tex]n_1,M_1\text{ and }V_1[/tex] are the n-factor, molarity and volume of acid which is [tex]HA[/tex]

[tex]n_2,M_2\text{ and }V_2[/tex] are the n-factor, molarity and volume of base which is NaOH.

We are given:

[tex]n_1=1\\M_1=?\\V_1=15.00mL\\n_2=1\\M_2=0.1036M\\V_2=17.73mL[/tex]

Putting values in above equation, we get:

[tex]1\times M_1\times 15.00=1\times 0.1036\times 17.73\\\\M_1=0.1224[/tex]

Thus the concentration (in M) of the weak acid in the sample is 0.1224

The concentration of the weak acid, HA in the sample is 0.123 M

We'll begin by calculating the number of mole of NaOH in the solution. This can be obtained as follow:

Molarity of NaOH = 0.1036 M

Volume = 17.73 mL = 17.73 / 1000 = 0.01773 L

Mole of NaOH =.?

Mole = Molarity x Volume

Mole of NaOH = 0.1036 × 0.01773

Mole of KOH = 0.00184 mole

  • Next, we shall determine the number of mole of weak acid, HA that will react with 0.00184 mole of NaOH. This can be obtained as follow:

HA + NaOH —> NaA + H₂O

From the balanced equation above,

1 mole of HA reacted with 1 mole of NaOH

Therefore,

0.00184 mole of HA will also react with 0.00184 mole of NaOH.

  • Finally, we shall determine the concentration of the weak acid, HA. This can be obtained as follow:

Mole of HA = 0.00184 mole

Volume = 15 mL = 15 / 1000 = 0.015 L

Concentration of HA =?

Concentration = mole / Volume

Concentration of HA = 0.00184 / 0.015

Concentration of HA = 0.123 M

Therefore, the concentration of the weak acid, HA in the sample is 0.123 M

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