Analyzing an Acid Spill

Background Information :
Sulfuric acid is a dense, colourless, oily, corrosive liquid that is soluble in water prepared industrially by the reaction of water with sulfur trioxide. The formula H2SO4, displays that there are two hydrogen atoms and one sulphate polyatomic ion. Sulfuric acid has a pH level of 1, which means it is extremely acidic and has a large amount of H+ ions. It is widely used in the manufacture of chemicals, like in making hydrochloric acid, nitric acid, sulfate salts, synthetic detergents, dyes and pigments, explosives, and drugs. (Mansur G. Abdullah, 2014).
Sulfuric acid is manufactured by a long process that starts with sulfur being burned with access to oxygen and creating sulfur dioxide. This new compound is then oxidized to form sulfur trioxide. Also the sulfur trioxide of sulfuric acid occur s when sulfur dioxide reacts with oxygen and water. The balanced chemical equation is 2SO2 + O2 + 2H2O → H2SO4. (Mansur G. Abdullah,2014) The hazards involved with storing and transporting sulphuric acid are that it is highly corrosive therefore it will destroy or damage other substances that come in contact with it. This is very hazardous towards humans, animals and the environment. Sulphuric acid can also produce sulfur dioxide, which can be absorbed by plants and consumed by living organisms.
If there is a sulfuric acid spill in a river, the sulfuric acid changes the pH level in the water from 7 to approximately 1. This makes the water extremely acidic and highly toxic for all the living organisms because it can kill off huge populations of fish. It is also toxic for humans because the river water can leak through to ground water sources and contaminate well water. Another example is that when it is evaporated into the atmosphere it creates acid rain. The sulphuric acid rain then contaminates the habitats of plants and animals. When in contact with sulphuric acid it corrodes roads and other substances it comes in contact with, so all people must be evacuated and moves into a safer location. If there happens to be an acid spill on land, Some chemicals released may result in health hazards such as fires or explosions. Other chemical releases may present health threats because of their ability to spread rapidly and enter the body. Spills may release into the atmosphere, discharge into the sewer system, or leak directly into soils or surface water. It is necessary to notify the appropriate authorities if a spill has the potential to cause environmental damage, and evacuate the area if there are people nearby, because the people near could be effected or harmed by the chemicals. (J,Heweit,2013)

Testable Question: What is the effect of time (days) on the pH levels of sulfuric acid samples that were collected from the river.
Variables:
Independent Variable: Time (Days)
Dependent Variable: The acidity of the sulfuric acid solution (Sodium Hydroxide Drops)

Control Variables: Controls: | How it will be controlled: | Why: | Amount on bromothymol blue | 8 drops | If there is the same amount of bromothymol blue added in each test tube then it is ensured that there will be a constant colour being compared during the test. | Air temperature | 20 degrees Celsius (room temperature) | The higher the temperature the more it speeds up reactions because the particles collide faster. | Amount of sulphuric acid | 10mL | If there is the same amount of sulphuric acid added into each test tube then it is ensures that there will be a constant substance being compared during the test. |

Hypothesis:
If the time Increases, the acidity of each solution will decrease and the amount of sodium hydroxide it takes to neutralize the sulfuric acid solution to a pH of 7 will decrease because the pH levels of the sulfuric solution will be less each day as it moves downstream and breaks down.

Safety: Sulfuric acid and sodium hydroxide are corrosive liquids. Close toed shoes should be worn. If sulfuric acid comes in contact with combustible materials, it may cause a fire or an explosion. If sulfuric acid or sodium hydroxide is spilled on skin, eyes or face, wash immediately with cold water Do not inhale or swallow sulfuric acid or sodium hydroxide.
Materials:

Materials | Chemicals | Goggles | Dilute sodium hydroxide | Pipette | Bromothymol blue indicator | 125mL Erlenmeyer flask | Seven contaminated river water samples labeled from day 1 to day 7 | 10 mLGraduated cylinder | |

Procedure: 10 mL of the Day 1 sulfuric acid and water solution was measured into a graduated cylinder The 10 mL of solution was transferred into an Erlenmeyer flask. Seven drops of bromothymol blue indicator was then added into the solution. Sodium hydroxide was added drop by drop into the solution, drops were counted until the solution was neutralized. The solution was stirred multiple times until the colour remained constant. Neutralized solutions were then poured down the drained and cleaned. Two more trials were then repeated for the day one solution. Steps 1-7 were repeated with day 2 – day 7 solutions. When the experiment was completed, all lab equipment and lab stations were cleaned up with soap
Observations:
Table 1: Qualitative observations of Sulfuric Acid and Sodium Hydroxide DAYS | Before Sodium hydroxide was added | When bromothymol blue was added | During sodium hydroxide reaction | After sodium hydroxide reaction | Days 1 through 6 | Clear Colourless Liquid | Dark yellow Liquid | Splashed blue Returns to yellow | Light green Clear | Day 7 | Clear Coulourless liquid | Blue Liquid | Remains blue Becomes a darker shade | Dark Blue |

Table 2: Quantitative Observations: Of Acidity vs. Time
The acidity of the sulfuric acid solutions (Number of sodium hydroxide drops) Time (Days) | Trial 1 | Trial 2 | Trial 3 | AVG | 1 | 330 | 360 | 325 | 338 | 2 | 275 | 264 | 280 | 273 | 3 | 70 | 82 | 58 | 70 | 4 | 50 | 36 | 25 | 36 | 5 | 11 | 15 | 20 | 15 | 6 | 2 | 2 | 2 | 2 | 7 | 0 | 0 | 0 | 0 |
Discussion:
The amount of sulfuric acid added each day, needed to be kept constant to ensure that the test was fair because it would take more drops of sodium hydroxide to neutralize the sulfuric acid solution, if there was more sulfuric acid solution in one day, than in another. It would take more sodium hydroxide drops if there was a larger quantity of the sulfuric acid solution because there are more H+ ions . Also, The amount of bromothymol blue drops had to be kept constant so the same green shade when the solution was neutralized and the results would be observed easier. Lastly the air temperature had to remain at 20 degrees Celsius throughout the entire experiment so each trial was fair.
The acidity and the number of drops of base required is an decrease- decrease relationship. This is known because when the level of acidity in the river decreases each day, the number of sodium hydroxide drops also decrease, as shown in table 2.
The shape of the graph is a negative non-linear correlation. The decrease in the acidity of the solutions is the largest from day 1 to day 2 and the acidity of the solution decreases at a slower rate from day 4 to day 7. this graph says that the acidity of the river in day 1, is the most extreme because the oil spill very recently occurred and the oil was at its greatest concentration. By day 2 the soloution was only about half as acidic because the river broke down the acid as it travelled down stream. There was a slow decrease from day 4 to day 7 where the water was completely neutral because the river had difficulty breaking down every last drop of acid.
It took 7 days for the river to return to a neutral pH of 7 and for the bromothymol blue to be green without using drops of a base to neutralize the acidity as displayed in table 2.
Adding sodium hydroxide to the samples helps to determine the acidity because sulfuric acid is an acid that is very strongly acidic, so it will take more drops of sodium hydroxide to neutralize the solution to a pH of 7. If the sulphuric acid solution has an acidity that is already close to 7, it will take a very small number of drops to increase the pH levels so they are neutralized.
This method of determining acidity is fairly accurate because it gives a general result that shows if the river samples were highly acidic or moderately acidic after the acid spill. A few faults in the method are that it does not give you the exact pH level of the solutions which doesn't give you a very detailed result. Not to mention, during the test it was very difficult to see when the solution was green. It was difficult to obtain the faint green colour of a neutral solution. During a trial for day 6, the solution was completely yellow after the first drop, but when the second drop was added, the solution turned into a bright blue. This means that the sodium hydroxide never fully neutralized the sulfuric acid during the trials because only half of a drop was needed.
The observations would differ if calcium hydroxide was used instead of sodium hydroxide in this experiment because calcium hydroxide would form calcium sulphate solid as a product. A new precipitate would form inside the Erlenmeyer flask, which would make it more difficult to observe the changes of colours representing the acidity of the solution. This would occur because calcium sulphate is a solid at room temperature and sodium sulphate is aqueous at room temperature. Also calcium hydroxide is less basic and has a pH level of 12.4 and sodium hydroxide is more basic and has a pH level of 14. Therefore, it would take a greater amount of calcium hydroxide drops to neutralize the solution, which would make the procedure longer and it would take more time to observe changes within the reaction.
Neutralization Reaction in this experiment:
H2SO4 (aq) + NaOH (aq) → 2H2O (l) + CaSO4 (aq)
Neutralization reaction of sulfuric acid with calcium hydroxide:
H2SO4 (aq) + Ca(OH)2 (aq) → 2H20 (l) + CaSO4 (s)
The results of the lab were very comparable to the prediction. The hypothesis states that if the time increases, the level of acidity of each solution will decrease and the amount of sodium hydroxide it takes to neutralize the sulfuric acid solution to a pH of 7 will decrease as well. The observation table and the graph support the hypothesis because as the days increase the average number of sodium hydroxide drops decreases forming a negative correlation.
The design for this experiment was adequate because the procedure was simple and easy to follow, all of the safety precautions were taken and the two observation tables were organized as the results precisely. The results are adequate because for every day there were 3 trials performed. There was a 35 drop difference range between the day one trials to a 3 drop difference between the day 7 trials. The average of all three trials was calculated to obtain a number that was as close as possible to being correct. A source of error was counting the number of drops that were added into the solution. Some drops were bigger than other drops and some drops came out of the pipette very fast, so it was difficult to keep track of every one. Therefore there may be a possibility that there was inaccuracy when using the pipette in this experiment. This error also occurs for the bromothymol blue that was added into the solution. Some of the blue drops were bigger than others so there may be some trials with more bromothymol blue than other trials. These small errors may have slightly affected the results. The solution would never remain a constant green so it was never fully neutralized. The number of drops would not be correct for the trial because the number counted made the solution basic.
Some improvements to the procedure would be to fully clean the Erlenmeyer flask between each trial. The trials were disposed down the drain after they were neutralized then the erlenmeyer flask was refused for the next trial. There could be some remaining neutralized solution left inside the flask that could affect the results for the next trial. Some improvements to the experimental design would be to use more sulfuric acid solution (30 mL) in every trial. By using more solution it will give a more accurate result. It would be easier to neutralize the sulfuric acid solution because when 15 mL of the solution was used the test tube would be a clear yellow, but when one more drop was added the solution turned into a dark blue. If there was more sulfuric acid solution, then there needs to be more drops of sodium hydroxide, which means more drops to be added in the test tube and it will be easier to determine when the solution is neutral. This means it would give a more accurate result. One last improvement would be to measure the specific amount of bromothymol blue in a graduated cylinder that was added into the solution instead of dropping the liquid into the flask because the measurement of bromothymol blue would remain constant every trial. The dropper is slightly inaccurate with the size of the drops therefore the results would be more accurate using a graduated cylinder to measure the bromothymol blue. The same thing applies to the sodium hydroxide because by using a pipette the drops may come out in larger or smaller sizes, which isn't an exact measurement. By using the graduated cylinder, it gives you and exact amount, and it keeps the amount of sodium hydroxide constant for every trial.

Conclusion:
The effect of time (days) on the acidity levels of the sulfuric acid solution samples that were collected from the river is that as the time increases, the levels of the sulfuric acid increases as well. As the days go by, the river breaks down all the acid from the acid spill and then it travels downstream so it is neutralized. Therefore the acidity levels increase because in the day 1 trials, the acid starts out very acidic with a pH level of approximately 1 and in the day 7 trials, the acid is completely neutralized to a pH of 7. The acidity level increased by 6 during the whole experiment. Finally, the effect of time on the acidity levels of the sulfuric acid increased as well which was tested using drops of sodium hydroxide.

Works Cited:
The Editors of Encyclopædia Britannica, Mansur G. Abdullah , M. G. (n.d.). sulfuric acid (chemical compound). Encyclopedia Britannica Online. Retrieved April 9, 2014, from http://www.britannica.com/EBchecked/topic/572815/sulfuric-acid
Heweit, J. (n.d.). Emergency Planning for Chemical Spills - EPCRA Guide for Facilities. Emergency Planning for Chemical Spills - EPCRA Guide for Facilities. Retrieved April 9, 2014, from http://www.chemicalspill.org/EPCRA-facilities/spill.html