## Experimental Data

1)pH

pH of the samples:

2) Alkalinity measurement: SAMPLE #1:

Volume of water sample:_

Titrant:_Titrant concentration:_

 mL of titrant pH mL of titrant pH

Volume of titrant to reach pH Volume of titrant to reach pH

SAMPLE #2: Volume of water sample: Titrant:__

Titrant concentration:

 mL of titrant PH mL of titrant pH

Volume of titrant to reach pH = 8.3:_

Volume of titrant to reach pH = 4.5:_

SAMPLE #3:

Volume of water sample:_

Titrant:_Titrant concentration:

 mL of titrant pH mL of titrant pH
 mL of titrant pH mL of titrant pH

Volume of titrant to reach pH= 8.3:_

Volume of titrant to reach pH= 4.5:_

SAMPLE #4:

Volume of water sample:_

Titrant: Titrant concentration:

 mL of titrant pH mL of titrant pH

Volume of titrant to reach pH Volume of titrant to reach pH

SAMPLE #5:

Volume of water sample:_

Titrant: _Titrant concentration:_

 mL of titrant pH mL of titrant pH

Volume of titrant to reach pH = 8.3:_

Volume of titrant to reach pH = 4.5:_

PART A. Data analysis:

1. From the experimental data obtained with each sample tested, report the alkalinity values and the concentration of each alkalinity species present (as mg/L of CaCO^).

Why is distilled water considered to have no buffering capacity?

To calculate the alkalinity, apply the following formula:

(V acid, mL) (M, acid solution)(100 g/mol CaC03) (1000 mg/g)

Alkalinity, mg/L CaC03 =

 Sample P-Alkalinity as CaC03 M-Alkalinity as CaC03 Total Alkalinity as CaC03 #1 #2 #3 #4 #5

To determine the approximate concentration of hydroxide, carbonate and bicarbonate ions in each sample, one can use the following relationships and assumptions:

 Volume of titrant to reach the endpoint Predominant chemical species Concentration of the chemical species vp = o HCO^ = M alkalinity VM= 0 OH" = P alkalinity II £ cor = P alkalinity VP > VM cor = (P — M) alkalinity = M alkalinity Vp < Vm and the pH is between 8.2-9.6 HCO^ = 2P alkalinity = (M — 2P) alkalinity Vp < VM and pH > 9.6 OH- = 2(M - P) alkalinity = (2P - M) alkalinity

Note: The P (Phenolphthalein) endpoint = pH 8.3, and the M (methyl orange or bromocresol green) endpoint = pH 4.5.

Note: The P (Phenolphthalein) endpoint = pH 8.3, and the M (methyl orange or bromocresol green) endpoint = pH 4.5.

The dominant species at 4.5 are assumed to be bicarbonate and carbonate, and when OH- ions are present, no bicarbonate ions can be present. It is also assumed that [H+] is not relevant in alkaline pH values, and that one half of the carbonate ions present become neutralized at the 8.3 endpoint. With the above information, determine the speciation of the alkalinity in each sample:

 Sample [H"] [Off] [HCO3-] [C032] m #2 #3 #4 #5

2. Observe the differences between the values of these samples and indicate what has influenced the composition of these samples.

Tap water

D.I. water

3. Based on the experimental values of ANC obtained with the different samples, classify these samples according to their sensitivity to acid discharge.

 Sample Sensitivity Justification #1 #2 #3 #4 #5

PARTB. BUFFERING CAPACITY

B.l.a EXPERIMENTAL DATA

Volume of water sample:_

Titrant:_Titrant concentration:_

mL of titrant

pH

AVb

ApH

-

-

Volume of water sample:

Titrant:

Titrant concentration:

mL of titrant

pH | AVb

ApH

r

-

Volume of water sample:

Titrant:

Titrant concentration:

mL of titrant

pH

AVb

ApH

-

-

Volume of water sample:_

Titrant: _Titrant concentration:

 mL of titrant pH AVb ApH - -

B. Lb Determine the buffering capacity of each sample:

For this purpose, you must consider the largest volume of base added in order to raise the pH by one unit. Then, convert this volume into moles of base consumed per initial volume of buffer (considered in liters).

 Sample Buffering capacity #1 #2 #3 #4 #5

Which of the measured samples has the highest buffering capacity? At what pH does this solution buffer?_

B.2 Factors that affect the buffering capacity B.2.A

Buffer:_

Volume of sample:_

Titrant:_Titrant concentration:

 mL of titrant PH AVb ApH 0 -
 mL of titrant pH AVb ApH

Estimate the pH value at which the maximum rate of change of pH per unit of volume (i.e., ApH/A V) occurs:_

Buffer B.2.2

Buffer:_

Volume of sample:_

Titrant:

Titrant concentration:

 mL of titrant pH AVb ApH

Estimate the pH value at which the maximum rate of change of pH per unit of volume (i.e ApH/AF) occurs:_

Buffer B.2.3

Volume of sample:_

 mL of titrant pH AVb ApH - -

Estimate the pH value at which the maximum rate of change of pH per unit of volume (i.e., ApH/AF) occurs:_

Butter B.2.4

Volume of sample: __

Titrant: _ Titrant concentration:_

mL of titrant

pH

AVb

ApH

-

-

Buffer:_

Titrant:_Titrant concentration:_

 mL of titrant pH AVb ApH - -

B.2.b.l Determine the buffering capacity ofeach sample:

For this purpose, you must consider the largest volume of base added in order to raise the pH by one unit. Then, convert this volume into moles of base consumed per initial volume of buffer (considered in liters).

 Buffer Buffering capacity B.2.1 B.2.2 B.2.3 B.2.4 B.2.5

Which of the measured samples has the highest buffering capacity? At what pH does this solution buffer?_

B.2.b.2 Determine theoretically the btffering index of each of the buffers mentioned above.

 Buffer Buffering Index B.2.1 B.2.2 B.2.3 B.2.4 B.2.5
 Buffer Buffering Index B.2.1 B.2.2 B.2.3 B.2.4 B.2.5

Include the pertinent graphs and calculations.

B.2.b.4 Relate the differences in composition of the different buffers to the corresponding responses: pH, buffering capacity, buffering index. What do you conclude With respect to their differences and responses?

PARTC: CALCULATION, PREPARATION, AND EVALUATION OF A SPECIFIED pH BUFFER SOLUTION

Include all the calculations needed to arrive at the composition and volumes used in the preparation of the corresponding buffer:

C. l.a Acid buffering capacity

Buffer:_

 mL of titrant PH AVb ApH

Estimate the pH value at which the maximum rate of change of pH per unit of volume (i.e. ApH/AF) occurs:_

C. l.b Base buffering capacity

Buffer:_

Titrant: _Titrant concentration:

 mL of titrant PH AVac ApH

C.2.a How does the experimental pH value ofthe buffer SQlution that you prepared compare with the theoretical pH? Is there a deviation greater than 0.5 pH units? Why do you think this is so?

C.2.b Determine experimentally the acid and base buffering capacity of your buffer solution: For this purpose, you must consider the largest volume of base added in order to raise the pH by one unit Then, convert this volume into moles of base consumed per initial volume of buffer (considered in liters).

 Buffering capacity Acid Base

Considering the other buffers prepared in part B, how does yours compare in buffering capacity? C.2.b.2 Determine theoretically the buffering index of the prepared buffers.

 Buffer Buffering Index

Include all the equations and calculations.

C.2.b.3 Determine experimentally the buffering index of the prepared buffer.

 Buffer Buffering Index

Include all the pertinent graphs and calculations.

Include all the pertinent graphs and calculations.