Analysis of commercial bleach lab report

Pre-lab Safety Sodium Hypochlorite is a strong oxidizer. Irritating effects increase with the strength of solution and the time of exposure. Flush exposed skin with water for several minutes. Fumes are irritating to eyes and mucous membranes. DO NOT MIX CHLORINE BLEACH WITH toilet bowl cleaners, ammonia, lye, rust removers, vinegar, or oven cleaners. Do not mix chlorine with any other cleaning agent! The result can be a sudden release of TOXIC chlorine gas. Inhalation can cause serious injury or death. Potassium Iodate may cause skin irritation. As with all chemicals, wash hands thoroughly if skin is exposed. Use the eyewash if splashed in the eyes. Caution! Acids, such as H2SO4 are hazardous if splashed on clothing, exposed skin or in the eyes. Prolonged exposure of the skin to even fairly dilute solutions of acid and base can cause serious burns. If acids splash on skin or clothes, remove the affected clothing and flush the affected areas thoroughly with cold water. Disposal of Chemicals: All solutions may be disposed of in the sink with plenty of water. 1. List all of the chemicals you will use for this week's experiment. For each chemical, list specific safety precaution(s) that must be followed. In order to find specific safety information, please obtain a Materials Safety Data Sheet (MSDS) on the chemical of interest. MSDSs can be found through an internet search (e.g., google) or from the following website: www.hazard.com Read the MSDS and find specific safety concerns for each chemical. 2. Explain why chlorine bleaches should not be mixed with other household chemicals such as ammonia. 3. Define the following terms: primary standard, standard solution, equivalence point. 1 4. Why do you think the solid KIO3 that you will use to make your primary standard will be dried overnight in an oven? 5. Describe how 100 mL of 0.01 M KIO3 primary standard can be prepared from solid potassium iodate. Write a step-by-step procedure that includes supporting calculations and any equipment/glassware that is required. Keep in mind that the concentration of a primary standard must be accurately known, which could influence your preparation technique and choice of glassware. 6. What is an internal indicator? What is the internal indicator in the redox titrations carried out in this experiment? 7. Use the chemical reactions shown below to answer the following questions. IO3- (aq) + 5 I- (aq) + 6 H+ (aq) → 3 I2 (aq, brown/yellow) + 3 H2O (l) I2 (aq, brown/yellow) + 2 S O2 2-3 (aq) → 2 I- (aq, colorless) + S O 2-4(aq) 6 a. What is the stoichiometric relationship between IO3- and I2? b. What is the stoichiometric relationship between I2 and S2O32-? c. What is the stoichiometric relationship between IO3- and S2O32-? d. How will knowing these relationships help you calculate the molarity of the Na2S2O3 solution in Part 1 of this experiment? 2 Name: ___________________________________ Question Sheet – Determination of Sodium Hypochlorite in Bleach 1) Describe the methodology used to prepare the 0.01 M KIO3 primary standard solution. 2) Describe the method used to determine the concentration of NaClO in the household bleach solution. 3) Bottles of commercially available bleach are labelled with the concentration of NaClO by mass %. Find one of these NaClO mass % specifications on either an actual bleach bottle or, equally fine, on an online photo or manufacturer’s website. Compare this to the concentration value you determined by experiment. Explain possible reasons for a discrepancy. 4) In the titration your group completed today, why was it important to document the “exact” amount of bleach solution added to the titration vessel, but not important to record exactly how much distilled water was added to vessel? 5) Imagine that you are teaching a new chemistry student how to use a 100-mL-size volumetric flask to prepare a 0.1000 M solution of KIO3. Explain at least three essential points that you must make in properly training the new student. 6) Pretend that you are teaching a new chemistry student how to use a glass (volumetric) pipet to properly deliver 25.0 mL of KIO3 solution to a titration vessel. Offer three points that must be made in your training of the new student. 7) One lab group accidentally performed today’s titration experiment without diluting the “full strength” bleach. Without looking at this group’s actual data, make a rough prediction about how the volume of Na2S2O3 they had to deliver from their buret differed from the volume your group delivered. Do you think this student group ran into any problem that prevented them from completing their Part 2 titration trials in a consistent or timely manner? Explain. 8) Bleach must never be mixed with other cleaning agents: the consequences can be fatal. Give the name and chemical formula for a highly toxic gas that can be released if bleach were unfortunately mixed with another cleaning agent. Determining the Mass Percent of Sodium Hypochlorite (NaClO) in Bleach Introduction The active ingredient in most chlorine bleaches is sodium hypochlorite, NaClO. The purpose of this two-part experiment is to determine the mass percent of sodium hypochlorite in a commercial chlorine bleach sample.