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Chemistry 14.1 Formal Lab Report

Experiment no. 7 Acids Bases and Salts

Javin Benedicto

on 18 March 2011

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Transcript of Chemistry 14.1 Formal Lab Report

Chem 14.1 Lab Report Experiment 7
Acids, Bases and Salts THE END Abstract Topic Techniques Relevant Data Results Introduction Keywords Acids Bases Electrolytes Titration & Objectives The objectives of this experiment are as follows:•To determine whether a solution is an acid or a base using different indicators•To classify electrolytes of a solution into weak or strong and be able to relate it to its conducting properties•To calculate the molarity, volume and concentration of a given solution•To identify the endpoint of an acid-base titration Significance The significance of the experiment is to show the properties of some solutions through the strength of their acidity or basicity. substances whose aqueous solutions contain ions
Includes: Acids Bases and Salts Salts pH sour taste
proton donors
pH less than 7 the products of the neutralization reaction between the acids and bases are the salts. They are the combination of the cation of the base plus the anion of the acid. bitter taste
proton acceptor
pH greater than 7 a measure of the acidity
pH = -log [H] method of quantitative chemical analysis that is used to determine the unknown concentration of a known reactant Experimental Materials The Experiments The materials used for this experiment include the following: 0.1 M sodium chloride (NaCl), 0.1 M ammonium chloride (NH4Cl), 0.1 M sodium hydroxide (NaOH), 0.1 M Acetic acid (HC2H3O2), 0.1 M Hydrochloric acid (HCl), 0.1 M sucrose (C12H22O11), 1 M Hydrochloric acid (HCl), 1 M sodium hydroxide (NaOH), 1 M Acetic acid (HC2H3O2), ethyl alcohol (C2H5OH), litmus paper, pH paper, sodium hydroxide pellets, congo red and phenolphthalein. Electrolytes Conductivity Test Preparation of 0.1 M NaOH using NaOH pellets Preparation of 0.1 M NaOH from available concentration of NaOH Titration of an Acid with a Base Five drops each of 0.1 M NaCl, 0.1 M NH4Cl, 0.1 M NaOH, 0.1 M HC2H3O2, 0.1 M HCl, 0.1 M C12H22O11, C2H5OH and Distilled were taken and tested with litmus paper, phenolphthalein and congo red. The researchers then took note of the color of the solutions and classified them into acids, bases and neutral salts. The conductivity of the solutions was tested using a conductivity apparatus. The apparatus consists of a light bulb, a plug and electrode rods. The apparatus was plugged into an outlet (power source of the apparatus). The electrodes were then rinsed with distilled water to avoid biases in the results of the test. The solutions were placed in a 50-mL beaker and tested with the conductivity rods. The weight of NaOH pellets required to prepare 100.0 mL of 1 M NaOH was calculated. After the computation, the computed weight of the NaOH pellets was weighed using a watch glass. This has to be done quickly since the NaOH pellets are hygroscopic, meaning NaOH pellets absorb water molecules from the air. This will affect the weight of the NaOH pellets.

The weighted amount of the NaOH pellets was then dissolved in 50 mL of water. The solution was then transferred into a 100-mL volumetric flask and diluted to the mark with distilled water.
The volume of NaOH needed to prepare 100 mL of 0.1 M NaOH from the concentration prepared earlier in the experiment was computed. The volume obtained was then placed in a 100-mL volumetric flask and diluted to mark. The base buret was washed thoroughly with soap and water and was rinsed three times with 3-mL portions of the standard base, 0.1 M NaOH. The buret was filled with 0.1 M NaOH. The air space at the tip was expelled and the reading was set to zero. The buret was clamped to the iron stand in preparation for titration.

10-mL of the unknown acid, prepared by the instructor, was transferred into an Erlenmeyer flask and diluted with 50-mL distilled water. Two to three drops of phenolphthalein was added. The acid was titrated with the standard base until the first appearance of a permanent light pink coloration.
Three trials of titration were conducted.
Results table Preparation of 0.1 M NaOH using NaOH pellets Calculations:
Molarity = mole (no. of moles of solute)
L (volume of solution)
Mole = Molarity x Volume
= 1 M (0.1 L) = 0.1 mole x ( 40.01 g NaOH)
(1 mol)
=4.001g NaOH
M1V1 = M2V2
M1= 1M
V1= 0.1 M (0.1L)/1 M
= 0.01L x (1000 mL)/1 L
V1=10 mL of 1.0 M NaOH Preparation of 0.1 M NaOH from available concentration of NaOH Titration of an Acid with a Base the REsults Discussion Experiment No. 7, entitled Acids, Bases and Salts basically has five set-ups. First Part classification of acid, bases, and salts using indicators and pH paper Second Part the conductivity test, is done to determine whether the solutions tested in the first part are weak or strong electrolytes Third and Fourth The preparation of NaOH concentrations is done in the third and fourth step. Last Part using the 0.1 M NaOH as standard solution, the concentration of an unknown acid was calculated from the endpoint of an acid-base titration. Titration was used to determine the concentration of an unknown acid Guide Questions and Answers 1.From your results, what relationship can you draw between the acidity/ basicity of a substance and its electrolyte property? Strong acids, strong bases and salts are good conductors of electricity. These substances are completely ionized in the reaction process. Substances with complete ionization are good conductors and thus are called strong electrolytes.
On the other hand, weak acids and weak bases conduct electricity poorly. Weak acids and weak bases are poor conductors of electricity and are called weak electrolytes. 2. Why are electrolytes conductors of electricity? Electrolytes dissociate into positively and negatively charged ions in solution. Positively charged ions move toward the negative electrode and negatively charged ions move toward the positive electrode. This is equivalent to the movement of electrons along a metal wire, giving electrolytes their conductive property. 3. Calculate the pH of the following solutions: At equilibrium,
[OH-] = 1.34 x 10^-3 M

pOH = -log [1.34 x 10^-3]
= 2.87
pH = 14 – 2.87
= 11.13 Conclusions and Recommendations use indicators like phenolphthalein, congo red litmus paper and pH papers for classifying acidic, basic and neutral substances
the conductivity apparatus is used to classify electrolytes as weak or strong.
pH values - highly acidic or basic - strong acid/base - good conductor
Weak acids and bases are weak conductors of electricity.
In titration a solution of accurately known concentration, called standard solution, is gradually added to another solution of unknown concentration, until the chemical reaction between the two is complete. By determining the endpoint of an acid-base titration, the concentration of an unknown solution can be known.
calculations for the concentrations of NaOH should be correct for inaccuracy or else it might affect the results.

We recommend using indicators or pH papers if you are unsure of the acidity or basicity your sample, since tasting chemical solutions is not a good practice.
be aware of the cleanliness of the apparatuses used and the prevention of contamination of materials involved.
Titration should be carefully done as small amounts of liquid may vary the result completely.
Also, complete understanding of the computations for molarity and dilution is highly recommended for this experiment.
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