Vernier Software and Technology
Vernier Software & Technology

The Buffer in Lemonade

Figure from experiment 32 from Chemistry with Vernier


One important property of weak acids and weak bases is their ability to form buffers. A buffer is the combination of a weak acid and a salt of the weak acid. Acetic acid and sodium acetate are an example of this kind of buffer pair. Buffers resist changes in pH upon the addition of small amounts of H+ or OH ions. The dissociation equation for acetic acid contains both of the buffer components, HC2H3O2 and C2H3O2:

{\text{H}}{{\text{C}}_{\text{2}}}{{\text{H}}_{\text{3}}}{{\text{O}}_{\text{2}}}{\text{(aq)}} \leftrightarrow {{\text{H}}^{\text{ + }}}{\text{(aq)  +  }}{{\text{C}}_{\text{2}}}{{\text{H}}_{\text{3}}}{{\text{O}}_{\text{2}}}^{\text{ - }}{\text{(aq)}}

When a small amount of an HCl solution is added to the buffer solution, most of the H+ ions are removed when they react with acetate ions:

{{\text{H}}^{\text{ + }}}{\text{(aq)  +  }}{{\text{C}}_{\text{2}}}{{\text{H}}_{\text{3}}}{{\text{O}}_{\text{2}}}^{\text{ - }}{\text{(aq)}} \leftrightarrow {\text{H}}{{\text{C}}_{\text{2}}}{{\text{H}}_{\text{3}}}{{\text{O}}_{\text{2}}}{\text{(aq)}}

When a solution of NaOH is added to the buffer, most of the OH ions are removed when they react with acetic acid molecules:

{\text{O}}{{\text{H}}^{\text{ - }}}{\text{(aq)  +  H}}{{\text{C}}_{\text{2}}}{{\text{H}}_{\text{3}}}{{\text{O}}_{\text{2}}}{\text{(aq)}} \leftrightarrow {{\text{H}}_{\text{2}}}{\text{O(l)  +  }}{{\text{C}}_{\text{2}}}{{\text{H}}_{\text{3}}}{{\text{O}}_{\text{2}}}^ - {\text{(aq)}}

Buffers are incorporated into various consumer products to help control the effects of varying pH. The popular powdered drink mix used in this experiment uses a citric acid–sodium citrate buffer to “control acidity,” according to its label.


In this experiment, you will

  • Use a pH Sensor to monitor pH as you titrate a given volume of the commercial brand of lemonade drink.
  • Use a pH Sensor to monitor pH as you titrate an unbuffered solution of 0.010 M citric acid.
  • Compare the results of the unbuffered solution with the lemonade buffer system.

Sensors and Equipment

This experiment features the following Vernier sensors and equipment.

Option 1

Option 2

Additional Requirements

You may also need an interface and software for data collection. What do I need for data collection?

Standards Correlations

See all standards correlations for Chemistry with Vernier »

Chemistry with Vernier

See other experiments from the lab book.

1Endothermic and Exothermic Reactions
2Freezing and Melting of Water
3Another Look at Freezing Temperature
4Heat of Fusion of Ice
5Find the Relationship: An Exercise in Graphing Analysis
6Boyle's Law: Pressure-Volume Relationship in Gases
7Pressure-Temperature Relationship in Gases
8Fractional Distillation
9Evaporation and Intermolecular Attractions
10Vapor Pressure of Liquids
11Determining the Concentration of a Solution: Beer's Law
12Effect of Temperature on Solubility of a Salt
13Properties of Solutions: Electrolytes and Non-Electrolytes
14Conductivity of Solutions: The Effect of Concentration
15Using Freezing Point Depression to Find Molecular Weight
16Energy Content of Foods
17Energy Content of Fuels
18Additivity of Heats of Reaction: Hess's Law
19Heat of Combustion: Magnesium
20Chemical Equilibrium: Finding a Constant, Kc
21Household Acids and Bases
22Acid Rain
23Titration Curves of Strong and Weak Acids and Bases
24Acid-Base Titration
25Titration of a Diprotic Acid: Identifying an Unknown
26Using Conductivity to Find an Equivalence Point
27Acid Dissociation Constant, Ka
28Establishing a Table of Reduction Potentials: Micro-Voltaic Cells
29Lead Storage Batteries
30Rate Law Determination of the Crystal Violet Reaction
31Time-Release Vitamin C Tablets
32The Buffer in Lemonade
33Determining the Free Chlorine Content of Swimming Pool Water
34Determining the Quantity of Iron in a Vitamin Tablet
35Determining the Phosphoric Acid Content in Soft Drinks
36Microscale Acid-Base Titration

Experiment 32 from Chemistry with Vernier Lab Book

<em>Chemistry with Vernier</em> book cover

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