Buffers: Acid and Base

 Buffers

Jihyun Yoo

Testing Water as a Buffer

The pH of water before and after adding HCI

0mL HCI: 8.8

5mL HCI: 1.70

10mL HCI: 1.53

15mL HCI: 1.35

20mL HCI: 1.30

pH is getting lowered, becoming acidic

The pH of water before and after adding NaOH

0mL NaOH: 7.30

5mL NaOH: 12.62

10mL NaOH: 12.86

15mL NaOH: 12.98

20mL NaOH: 13.04

pH is getting higher, becoming basic

Explain the assertion and include a brief discussion on the buffering capacity of water.

Water acted as buffer because pH changed directly when we mix acid and base together

Making Buffer Solutions

Show all calculations for making your acidic buffer solution. Include the desired pH of your solution. 

Show all calculations for making your basic buffer solution. Include the desired pH of your solution. 

Based on how you created these buffered, explain how these can "buffer" the addition of H+ or OH-

    1) Acidic buffer: putting H+ will make the conjugate base to neutral while OH- will make the weak acid to neutral.

    2) Basic buffer: putting H+ will make the weak base to neutral while OH- make the conjugate acid to neutral. 

Testing Your Buffer's capacity

Acidic Buffer

Calculate the moles of HCI added to the acidic buffer before its buffering capacity was exceeded

    5 ml HCL x 10^-3 L/mL x 0.1 mol HCL = 0.0005 mol HCI

PH of an Acidic Buffer with Added Acid or Base

HCI Volume	pH	NaOH Volume	pH
(mL)	-	(mL)	-
0	0	0	4.2
5	3.88	5	4.5
10	2.47	10	4.9
		15	5.7

Calculate the moles of NaOH added to the acidic buffer before its buffering capacity was exceeded

10mL NaOH x 10^-3 L/mL x 0.1 mol NaOH = 0.001 mol NaOH

Briefly explain how the acidic buffer was capable of buffering these amounts of HCi and NaOH

At first, when I make HCI react with conjugate base, it would make acetic acid which neutralizes HCI

Secondly, when I make NaOH react with acetic acid, it would make sodium acetate to be neutral

Basic Buffer

Calculate the moles of HCI added to the basic buffer before its buffering capacity was exceeded

20mL HCI x 10^-3 L/mL x 0.1 mol HCI = 0.002 mol HCI

pH of an Basic Buffer with Added Acid or Base

HCI Volume	pH	NaOH Volume	pH
(mL)	-	(mL)	-
0	10.01	0	10.01
5	9.87	5	10.18
10	9.67	10	10.42
15	9.44	15	10.62
20	9.1	20	10.9
25	8.35	25	11.41

Calculate the moles of NaOH added to the basic buffer before its buffering capacity was exceeded

20mL NaOH x 10^-3 L/mL x 0.1 mol NaOH = 0.002 mol NaOH

Explain how the basic buffer was capable of buffering these amounts of HCI and NaOH

The basic buffer was allowed to buffer the HCI and NaOH because HCI will react with conjugate base and sodium carbonate and all these reactions will finally form conjugate acid and sodium bicarbonate to neutral. In addition, putting NaOH will react with sodium bicarbonate, which forms sodium carbonate to neutral.

Beyond the Bench

The main goal of buffer is maintaining pH level changes. 

In our daily life, baby lotions will prevent your skin from expose of bacteria by maintaining pH level. 

The most common example of daily buffer is detergent for clothes washing which prevent their ingredients rom breaking down.