Introduction
Acids and bases are chemicals with a wide range of applications both industrially and on small-scale basis. According to Arrhenius, an acid is a substance that liberates H+ when placed in water (Slabaugh & Spencer, 167). On the other hand, a base is a substance that liberates OH- when placed in water (Slabaugh & Spencer, 167). To illustrate, pure water dissociates partially to produce hydrogen ions and hydroxide ions as shown in the equation below:
H2Ol H+aq+ OH-aq
In the above equation, water dissociates to produce H+ and OH-. If an acidic substance is placed in water, it reacts with water to produce H+. The resulting solution is acidic because it contains more H+ than the OH-. On the other hand, a basic substance reacts with water to produce more OH- than H+. Consequently, the solution is said to basic.
Brownsted Lowry came up with a different definition of an acid from the definition proposed by Arrhenius. In this case, Brownsted defines acid as substances that donate H+ (protons) (proton donors) (Moore & Conrad, 607). On the other hand, bases refer to substances that accept H+ (protons)(proton acceptors). These definitions can be illustrated using the equation of auto-ionization of water shown below:
H2Ol+ H2O l H3O+aq+ OH- aq
In the above reaction, one molecule of water donates one H+, a proton, while the other molecule accepts the proton. The molecule that donates a proton behaves as an acid. Therefore, it can be referred to as an acid based on Lowry’s definition. On the other hand, the molecule that accepts the H+ behaves as a base. Consequently, it is referred to as a base in this case.
Buffers are chemical substances that can donate or receive protons, but their pH values are not changed significantly when acids or bases are added. Buffers can maintain a fairly constant pH if the amount of acids or bases added does not exceed a specified limit. This limit is referred to as the buffer capacity. An example of a buffer solution is the solution consisting of equal amounts of formic acid (HCHO2) and its salt, sodium formulate (NaCHO2).
Hypothesis
The following hypotheses were tested in the experiment:
Ha: Sodium chloride is one of the products formed when sodium hydroxide solution reacts with hydrochloric acid
H0: Sodium chloride is not one of the products formed when sodium hydroxide solution reacts with hydrochloric acid
Ha: The pH values for lemon juice, orange juice, and milk are less than 7 while the pH value of saliva is greater than 7
H0: The pH values for lemon juice, orange juice, and milk are not less than 7 while the pH value for saliva is not greater than 7
Purpose
This lab sought to provide insights into the various aspects of acids, bases, and buffers. This report discusses three experiments performed in this lab. The first experiment (Experiment A) was aimed at investigating a neutralization reaction between sodium hydroxide and hydrochloric acid. The second experiment (Experiment B) was intended to measure the pH of lemon juice, orange juice, milk, and saliva. The third experiment (Experiment E), on the other hand, was aimed at investigating the properties of buffer solutions regarding their ability to maintain a fairly constant pH.
Materials
The following materials were used in the three experiments performed in this lab:
Apparatus
10mL graduated cylinder
10-cm test tube
Plastic droppers
Evaporating dish
Filter paper
Glass stirring rod
Burner
Long range pH paper
Reagents
1M NaOH
1M HCl
0.1M silver nitrate solution (AgNO3)
Lemon juice
Orange juice
Milk
Saliva
0.1M sodium acetate solution (NaC2H3O2)
0.1M acetic acid solution (HC2H3O2)
0.1M Aqueous ammonia solution (NH3)
0.1M ammonium chloride solution (NH4Cl)
Data/Table/Error Analysis/Conclusion
Data
Experiment A: Neutralization reaction
The data for the Acid-base neutralization reaction is shown in table 1 below:
Experiment B: pH Measurement
Experiment E: Buffer solutions
The results of the experiment involving solutions A, B, C, D, and boiled distilled water are shown in table 4 below:
Sources of error in this lab could have been the inadequate mixing of the contents using the plastic dropper.
Answers to Questions
Experiment A
The salt produced by the neutralization reaction between sodium hydroxide (NaOH) and hydrochloric acid (HCl) is sodium chloride (NaCl)
The equation for the reaction that took place when HCl and NaOH reacted is shown below:
NaOH aq+ HCl aq → NaCl aq+ H2O aq
Experiment B
The order of the substances tested in order of decreasing pH is as follows: Detergent (dishwashing), buffered aspirin, household ammonia, detergent (laundry), baking soda, milk, saliva, orange juice, aspirin, and lemon juice.
Answers to Questions
c.Li2SO4
Reason: Lithium is a group 1 element. Therefore, it has a valence of 1. On the other hand, sulphate radical has a valence of 2.
c. basic
Reason: they all have pH values that are greater than 7
c. CA + H2O COH + A- + H+
Reason: The reaction gives H+
a. Add equal amounts of acid to each solution until the pH of one solution changes significantly
Reason: When you add acid to all the solutions continuously, the solution with the greatest buffering capacity will be the last whose pH will change significantly. On the other hand, the solution with the least buffering capacity will be the first whose pH will change significantly.
Works Cited Top of FormTop of Form
Moore, John W, and Conrad L. Stanitski. Chemistry: The Molecular Science. , 2014. Print.
Slabaugh, Michael R, and Spencer L. Seager. Safety-scale Laboratory Experiments for Chemistry for Today. Pacific Grove, Calif: Brooks/Cole, 2013. Print.
