This is acids, bases, buffers and salts lab... Pour 50 mL of 0.10 M HCl in the f

Question

This is acids, bases, buffers and salts lab...

Pour 50 mL of 0.10 M HCl in the first beaker.

Pour 5.0 mL of this solution into your clean, dry 100 mL graduate cylinder. Add distilled water until the 50.0 mL mark and pour the mixture into the second beaker and mix well.

Pour 5.0 mL of the solution in the second beaker into the graduate cylinder and dilute this to 50.0 mL. Pour this into the third beaker and mix well. and repeat the procedure using 0.10M NaOH.

PH(HCl) : beaker #1: 4.7 #2: 4.3 #3: 2.3

PH(NaOH) : beaker #1 : 12.3 #2: 11.6 #3: 10.9

(1)Calculate the concentration of HCl or NaOH in each of the solutions you measured using the dilution equation: M1V1 = M2V2.

(2)By how many units did the pH of a solution of a strong base or acid change when it was diluted by a factor of ten?

Explanation / Answer

1. Case1: HCl

Beaker 1: concentration of solution = 0.1M

Beaker 2: M1V1 = M2V2

5mL x 0.1M = 50mL x M2

M2 = concentration of solution= 0.01M

Beaker 3:

M1V1 = M2V2

5mL x 0.01M = 50mL x M2

M2 =concentration of the solution = 0.001M

Case 2: NaOH

Same as HCl

2. pH

Case 1: HCl

pH = -log [H+]

beaker 1 : pH = - log [0.1M ] = 1

beaker 2: pH = -log [0.01M] = 2

beaker 3: pH = -log [0.001M] = 3

inference : as concentration of beaker 1: 2 increases by a factor of 10 (0.1/ 0.01) , pH increases from 1 to 2, that is by a factor of 1. Similarly, as concentration of beaker 2: 3 increases by a factor of 10 (0.01/ 0.001) , pH increases from 2 to 3, that is by a factor of 1. So, pH increases by a factor of 1 when concentration increases by a factor of 10 of a strong acid.

Case 2: NaOH

pOH = - log [OH-]

pH = 14 - pOH

beaker 1 : pOH = - log [0.1M ] = 1 , pH = 14-1 =13

beaker 2: pOH = -log [0.01M] = 2, pH = 14-2 = 12

beaker 3: pOH = -log [0.001M] = 3 , pH = 14-3 = 11

inference : as concentration of beaker 1: 2 increases by a factor of 10 (0.1/ 0.01) , pH decreases from 13 to 12, that is by a factor of 1. Similarly, as concentration of beaker 2: 3 increases by a factor of 10 (0.01/ 0.001) , pH decreases from 12 to11, that is by a factor of 1. So, pH decreases by a factor of 1 when concentration increases by a factor of 10 of a strong base.

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.