Project 7 acids and bases lab report

Project 7: The Properties of Acids and Bases

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Goals

The main goal of this project was to investigate the properties of the acids and bases by identifying four unknown substances. To identify the four unknown substances several experiments took place including a flame test, a pH test using litmus paper, and an ammonium test. After identifying each unknown, titrations were done to each to determine how much acid or base it takes to make the solution neutral. We also explored the concentration of different household chemicals to determine their acidic/basic features and purposes.

Experimental Design

For week 1 the team was four unknown solutions, sodium acetate, hydrogen chloride, ammonium hydroxide, and sodium hydroxide. The team performed cation and anion tests to determine what the unknown solutions could be. A flame test was performed to identify if the unknown solutions contained cations. To perform the test the team obtained a nichrome wire and heated it strongly in a bunsen flame to clean it. Then dipped the wire into the unknown solution and placed the nichrome wire over the flame. Once the nichrome wire was placed under the flame the team then analyzed the color the unknown solution produced. After recording the color we compared the results with the flame coloration chart. The team repeated these steps for each of the four unknown solutions. A pH test was performed to determine if the unknown solutions had acidic or basic properties. The pH was conducted by taking a litmus paper and dipping it into each solution. Then comparing the litmus paper to the pH chart to determine if the solution was basic or acidic. The next test performed was an ammonium test which consisted of taking 1 mL of the unknown solution and adding 1 mL of 6M NaOH and smelling the resulting mixture by wafting the air above the test tube gently towards your nose. If the smell of ammonia was present than that indicated the presence of ammonium ions. After performing these test the team then decided what the unknown solutions were based on the results and the choices given. The team repeated these steps for all four of the unknown solutions. The last procedure the team did in week 1 was titration of the now known solutions. To do this the team placed a beaker of the solution, which was 50 mL of diluted solution on top of a stirrer to keep the solution moving. Then a pipette dropped the acid or base into the solution while a device was used to measure the pH and the amount of drops. As the solution was titrated to equilibrium the data from the device was used to determine the pH and the concentration of the solution.

During week two, the team set out to determine the pH of our previously determined unknowns by way of titration. To determine the pH most accurately, the team used two methods of determining the pH. The first tactic was to use an indicator such as phenolphthalein in a diluted solution of the previously referenced unknown. The team started off with 5 mL of the various solutions and then diluted it to 50 mL with water. After the addition of a few drops of the indicator, phenolphthalein, the solution was titrated to saturation by either using a solution of cations or anions. If the solution was expected to be more acidic, anions were used. If the solution were expected to be more basic, cations were used. As more and more drops were added to the original solution, the color of that solution began to change. Once the solution was titrated to completion, in change in number of cations/anions solution was measured, and then used to determine how many cations/anions were necessary for the solution to reach a neutral pH. Similarly, the second way the team attempted to determine the pH of the solutions was by way of an electronic pH meter. The procedure is all the same as stated previously up until the addition of the indicator. Instead of the addition of an indicator, an electronic pH probe was inserted into the solution, and the team proceeded to titrate the solution until saturation. Once the solution was titrated, the team looked at a graph of the data and found the equivalency point. In other words, the point at which the pH reached 7. The team then used the computer program to measure the amount of titrant that was used to get the solution to that point. Once that was found, the same calculations as stated above were performed to determine the pH and the pOH of the original, unknown solutions.

The goal of week three was to determine the pH of several household chemicals and to observe how dilution affects the pH of one of our unknowns used in previous weeks. The household chemicals chosen were all drinks. The four-chosen included Coca Cola, Mello Yello, Sprite, and Orange Juice. Each of these drinks were subject to the same tests as listed above. Specifically, an electronic pH probe was used to obtain the most accurate reading. After the equivalency point was assessed, the pH was then calculated. As for the serial dilution of the unknowns, each of them were progressively diluted more and more using 1mL of the unknown substance and 10 mL of water and repeating this three times for each unknown substance then their pH was measured using Pasco software at each of the steps.

Results

· Identifying Unknown Substances Results [NaOH, HCl, NH4OH, CH3COONa]

Table 1: pH of the Unknown Solutions

Unknown Solutions

Litmus paper pH

Acid or Base

F1

10

Base

F2

1

Acid

F3

7

Neutral

F4

10

Base

Table 2: Cation Test/Flame Test

Unknown Substance

Flame Color

Indicates presence of...

F1

Colorless

F2

Colorless

F3

Orange

Sodium

F4

Orange

Sodium

Table 3: Ammonium Test

F1

No Smell

F2

Slight Smell

F3

No Smell

F4

Strong Smell

Table 4: Identification of Unknown Substance

Unknown Substance

Identity

F1

NaOH

F2

HCl

F3

CH3COONa

F4

NH4OH

· Calculation of Molarity and pH

Table 1: pH Calculation from Indicator

Unknown

pH

pOH

F1

14.045

-.045

F2

-.53

14.53

F3

9.4

4.6

F4

9.1

4.9

Table 2: pH Calculation from Pasco

Unknown

pH

pOH

F1

14.045

-.045

F2

.043

13.9

F3

9.4

4.6

F4

9.1

4.9

Table 3: Molarity Calculation from Indicator

Unknown

Molarity

F1

1.1099

F2

3.417

F3

1.1099

F4

.7063

Table 4: Molarity Calculation from Pasco

Unknown

Molarity

F1

1.099

F2

.9045

F3

1.1099

F4

.7063

· Dilutions

Table 1: Dilution of NaOH

F1--Strong Base

(NaOH)

pH found using PASCO probe

Dilution #1

12.51 pH

Dilution #2

11.66 pH

Dilution #3

10.55 pH

Table 2: Dilution of HCl

F2—Strong Acid

(HCl)

pH found using PASCO probe

Dilution #1

1.43 pH

Dilution #2

1.99 pH

Dilution #3

2.67 pH

Table 3: Dilution of CH3COONa

F3—Weak Acid

(CH3COONa)

pH found using PASCO probe

Dilution #1

6.85 pH

Dilution #2

7.11 pH

Dilution #3

7.20 pH

Table 4: Dilution of NH4OH

F4—Weak Base

(NH4OH)

pH found using PASCO probe

Dilution #1

10.75

Dilution #2

10.39

Dilution #3

9.74

· Titrations of Unknowns

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· Household Chemical pH and Titrations

Table 1: Litmus Test (pH) of the Household Chemicals

Unknown Solutions

Litmus paper pH

pH found with PASCO probe

Acid or Base

Coca Cola

5

4.99

Acid

Sprite

4

4.00

Acid

Mello Yello

4

4.95

Acid

Orange Juice

5

4.50

Acid

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