Acid Burn Lab

Experiment #5: Acid Burn!!!
Introduction
The goal of this lab was to correctly prepare a 0.2M solution of NaOH, identify highly acidic household cleaning chemicals, and determine their concentration (molarity) through titrations using the previously prepared 0.2M NaOH solution.
Experimental
First, to create 0.5L of 0.2M solution of NaOH, standard 3M NaOH solution was obtained. Next, calculations were performed to determine the amount 3M NaOH necessary to create 0.5L of the 0.2M solution and, as a result, 33.333ml of the 3M solution was measured and poured into a 600ml beaker. The 33.333ml of 3M solution was then diluted with deionized H2O to a volume of 0.5L, thus theoretically resulting in 0.5L of 0.2M NaOH. Next this solution was used
to titrate a sample of known mass of KHP dissolved in 40ml of deionized H2O indicator in order to determine the actual concentration of the experimental NaOH solution. Two trials of titration were conducted and the volumes of NaOH required to reach the equivalence point were recorded. Calculations yielded final concentrations for the NaOH solution of 0.1950M and 0.2005M respectively for an average concentration of 0.1977M; the experimental solution of NaOH was therefore concluded to be of sufficient quality for use in determining the concentration of the various household cleaners. In the determination of acidic household cleaning products, seven chemicals (Drano, SnoBol, glass cleaner, Parson’s, Lysol, The Works, and Comet) were presented. Each solution’s pH was determined using pH testing strips and the results were recorded. SnoBol, Lysol, and The Works each yielded pHs of 1, the most acidic of the seven chemicals, and, therefore, were selected for the final portion of the experiment in which their concentrations would be determined. To determine the concentrations (molarity) of SnoBol, Lysol, and The Works, 1ml of each chemical was diluted with 20ml of deionized H2O, treated with 3 drops of phenolphthalein indicator solution and titrated with the experimentally obtained 0.2M NaOH solution.
Multiple titrations were performed with each chemical. Calculations were then performed to determine the concentration of each chemical from its trials and the average molarities from these trials were used to conclude the concentration of each household cleaner. SnoBol had an average concentration of 4.7M, Lysol had an average concentration of 3.1M, and The Works had an average concentration of 6.3M.
Molarity of NaOH
Trial
Mass of KHP used (g)
NaOH used (ml)
Molarity of NaOH (mol/L)
1
0.6129
15.39
0.1950
2
0.6108
14.92
0.2005
Average Molarity of NaOH (M)
0.1977

Sample Calculations
Molarity of NaOH: 0.6129g KHP / (204.22g/mol) / (15.49ml/1000ml) = 0.1950
Average Molarity: (0.1950M + 0.2005M)/2 = 0.1977 pH of Household Cleaners
Cleaner
pH
Drano
11
SnoBol
1
Glass cleaner
9
Parson’s
9
Lysol
1
The Works
1
Comet
5

Molarity of Specific Household Cleaners
Product
Trial
NaOH used to titrate (ml)
Molarity of Product (mol/L)
Average Molarity of Product (g/L)
SnoBol
1
23.63
4.6724
4.6678

2
23.58
4.6625

3
23.61
4.6684

Lysol
1
15.98*
3.1597*
3.0797

2
15.56
3.0767

3
15.59
3.0826

The Works
1
33.08
6.5409
6.3162

2
31.54
6.2364

3
31.21
6.1712

*-Trial was discounted from final average because sample was overtitrated
Sample Calculations
Molarity of Household Cleaner: (33.08ml/1000ml) * (0.1977g/mol) / (0.001L) = 6.5409 mol/L

Concept Question 5B
Titrations allow a chemist to determine the concentration of a substance, called the titrand, by carrying out a reaction with known quantities such as volume, moles, and concentration of the titrant used.
In this experiment, a reaction between the acidic household cleaners and a standardized basic solution was used for the titration. In order to obtain standardization of the basic solution (NaOH), a specific volume of the substance was measured and diluted to an approximate concentration; the concentration of this resulting solution was then verified using titrations. Once the standardized NaOH solution was obtained, the household cleaner was first treated with a pH indicator (phenolphthalein) so that the equivalence point, the instant where exactly enough standard solution has been added to the titrand so that their molar concentrations are equal, could be seen. The equivalence point in the titrations conducted was equal to the end point, the instance at which the pH indicator changes color, which allowed the exact point of equivalence to be reached based on physical observation of the titrand. After the indicator had been added to the household cleaner being titrated, the titration was performed and the volume of NaOH required to reach the equivalence/end point was noted; the titration was then repeated twice more to ensure accuracy and precision. To determine the concentration of the household cleaner, first the volume of NaOH used to reach the equivalence point was
multiplied by the concentration of that standard solution which yielded the number of moles of household cleaner used, as it and the NaOH reacted in a 1:1 ration. Finally, the moles of household cleaner in the solution was divided by the volume (in liters) of the household cleaner used in the titration, thus yielding the overall concencration for the household cleaner.