b) Write a balanced equation for the reaction. One quick way to do this would be to figure out how many half-lives we have in the time given. Calculate the percent error between your average experimental value and theoretical value for the mass percent of oxygen in \(\ce{KClO3}\). Stoichiometry is a collective term for the quantitative relationships between the masses, the numbers of moles, and the numbers of particles (atoms, molecules, and ions) of the reactants and the products in a balanced chemical equation. The LibreTexts libraries arePowered by NICE CXone Expertand are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. Even though 2 mol of H2 are needed to react with each mole of O2, the molar mass of H2 is so much smaller than that of O2 that only a relatively small mass of H2 is needed compared to the mass of O2. These items are now known to be good sources of ascorbic acid. It finds widespread application as an iodide source because it is less hygroscopic than sodium iodide, making it easier to work with. This applies to all three parts of the experiment. extraction description. According to the balanced chemical equation, 6 mol of CO2 is produced per mole of glucose; the mole ratio of CO2 to glucose is therefore 6:1. You do not have enough time to do these sequentially and finish in one lab period. To experimentally determine the mass percent of oxygen in the compound potassium chlorate (\(\ce{KClO3}\)) via the thermal decomposition of a sample of potassium chlorate. Using molar masses along with the known formula of potassium chlorate, calculate the theoretical mass percent of oxygen in \(\ce{KClO3}\). Be careful to only select products where the actual vitamin C content in mg or percent of RDA (recommended daily allowance) is listed. Much more water is formed from 20 grams of H 2 than 96 grams of O 2. Show all your calculations on the back of this sheet. Dilute the solution to 250 mL with . These operations can be summarized as follows: \[ 45.3 \, g \, glucose \times {1 \, mol \, glucose \over 180.2 \, g \, glucose} \times {6 \, mol \, CO_2 \over 1 \, mol \, glucose} \times {44.010 \, g \, CO_2 \over 1 \, mol \, CO_2} = 66.4 \, g \, CO_2 \nonumber \]. The history of Vitamin C revolves around the history of the human disease scurvy, probably the first human illness to be recognized as a deficiency disease. You will need enough to make 500 mL of sample for use in 3-5 titrations. The two reactions we will use in this experiment are: \[\ce{KIO3(aq) + 6 H+(aq) +5 I- (aq) 3 I2(aq) + 3 H2O(l) + K+(aq) } \quad \quad \text{generation of }\ce{I2} \label{1}\], \[\underbrace{\ce{C6H8O6(aq)}}_{\text{vitamin C(ascorbic acid)}}\ce{ + I2(aq) C6H6O6(aq) +2 I- (aq) + 2 H+(aq) } \quad \quad \text{oxidation of vitamin C}\label{2}\]. The mixture is heated until the substance fully sublimates. The starting volumes in each of the burets should be between 0.00 mL and 2.00 mL. This is a redox titration. (s) Potassium iodate solution is added into an excess solution of acidified potassium. All these questions can be answered using the concepts of the mole, molar and formula masses, and solution concentrations, along with the coefficients in the appropriate balanced chemical equation. Some people become so proficient that they can titrate virtually "automatically" by allowing the titrant to drip out of the buret dropwise while keeping a hand on the stopcock, and swirling the solution with the other hand. Finding Mols and Masses of Reactants and Products Using Stoichiometric Factors (Mol Ratios): Finding Mols and Masses of Reactants and Products Using Stoichiometric Factors, YouTube(opens in new window) [youtu.be]. 2. temperature of the solution. (ii) determine the formula of the hydrated compound. Refill the buret between titrations so you wont go below the last mark. Note: You will need to bring a powdered or liquid drink, health product, fruit samples, or other commercial sample to lab for vitamin C analysis. The large cylinder in the middle contains the oxygen and hydrogen that fueled the shuttles main engine. Using a graduated cylinder, measure out at least 100 mL of your liquid sample. While adding the \(\ce{KIO3}\) swirl the flask to remove the color. Converting amounts of substances to molesand vice versais the key to all stoichiometry problems, whether the amounts are given in units of mass (grams or kilograms), weight (pounds or tons), or volume (liters or gallons). Thus 2 mol of H2 react with 1 mol of O2 to produce 2 mol of H2O. Potassium perchlorate, KClO_4 decomposes on heating to form potassium chloride and elemental oxygen. Show your calculations clearly. Add approximately 0.5-0.6 g of \(\ce{KI}\), 5-6 mL of 1 M \(\ce{HCl}\), and 3-4 drops of 0.5% starch solution to the flask. Students will perform a quantitative analysis of the reactants and products of this reaction, measuring the initial mass of solid potassium chlorate used (before heating), and the mass of the solid potassium chloride product, or residue, remaining after heating. Thermodynamic properties of substances. Why? The US space shuttle Discovery during liftoff. Scurvy is a disease unique to guinea pigs, various primates, and humans. . 50 mL of distilled water. B To convert tons of oxygen to units of mass in grams, we multiply by the appropriate conversion factors: \[ mass \, of \, O_2 = 1.00 \, tn \times { 2000 \, lb \over tn} \times {453.6 \, g \over lb} = 9.07 \times 10^5 \, g \, O_2 \nonumber \]. Glucose reacts with oxygen to produce carbon dioxide and water: \[ C_6H_{12}O_6 (s) + 6 O_2 (g) \rightarrow 6 CO_2 (g) + 6 H_2O (l) \label{3.6.1} \]. Fetch a stand and ring clamp from the back of the lab. 5. Titration 1. Developed countries use both potassium iodide (KI) and potassium iodate (KIO3) extensively for iodization of refined table salt. Color of precipitate produced by remains of test tube 1 mixed with AgNO3 6. Amount remaining after 4 days that is 96 hours=0.012 grams 4.93 g/cm 3. Oxygen is the limiting reactant. We use the same general strategy for solving stoichiometric calculations as in the preceding example. Place three medium-sized test tubes in the test tube rack. Accessibility StatementFor more information contact us atinfo@libretexts.orgor check out our status page at https://status.libretexts.org. Now use the coefficients in the balanced chemical equation to obtain the number of moles of H2 needed to react with this number of moles of O2: \[ mol \, H_2 = mol \, O_2 \times {2 \, mol \, H_2 \over 1 \, mol \, O_2} \nonumber \], \[ = 2.83 \times 10^4 \, mol \, O_2 \times {2 \, mol \, H_2 \over 1 \, mol \, O_2} = 5.66 \times 10^4 \, mol \, H_2 \nonumber \]. Forward reaction: 2I- + 2H+ Chlorine gas reacts with aqueous potassium iodide to form solid iodine and aqueous potassium chloride. All compounds consist of elements chemically . Add some distilled water to your crucible and. 5) Mass of hydrated salt mass of anhydrous salt = mass of water. 5.3: Stoichiometry Calculations is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by LibreTexts. Hint: you will need to use the approximate \(\ce{KIO3}\) molarity given in the lab instructions and the mole ratio you determined in the prior problem. grams H 2 O = (96 x 1/32 x 2 x 18) grams H 2 O. grams H 2 O = 108 grams O 2 O. 16) a) What of particles (atoms , molecules, cations, aNons, or canons anions) occupy the lattice in each of the crystalline solids given below. KMnO 4 + HCl = KCl + MnCl 2 + H 2 O + Cl 2. If it comes from a product label please remove the label and attach it to this report. Assume no heat loss to the calorimeter and assume the solution has a heat capacity of 4.18 J/0C.g. Be sure to use the average molarity determined for the \(\ce{KIO3}\) in Part A for these calculations. Its symptoms include exhaustion, massive hemorrhaging of flesh and gums, general weakness and diarrhea. What does the chemical formula KIO3 plus H2O plus Na2S2O5 produce? All compounds consist of elements chemically combined in fixed proportions they obey the Law of Constant Composition. In the late 1700's, the British Navy ordered the use of limes on ships to prevent scurvy. Vitamin C, known chemically as ascorbic acid, is an important component of a healthy diet. The best samples are lightly colored and/or easily pulverized. Wear safety glasses at all times during the experiment. Calculate the milligrams of ascorbic acid per gram of sample. Gold is extracted from its ores by treatment with an aqueous cyanide solution, which causes a reaction that forms the soluble [Au(CN)2] ion. The molar mass of H O is 1812 g/mol The reverse reaction must be suppressed. Dissolving KOH is a very large exotherm, Dissolving urea in water is . Using your average milligrams of Vitamin C per gram or milliliter of product from part C as the "correct" value, determine the percent error in the manufacturer or texts claim (show calculations)? Whether dealing with volumes of solutions of reactants or masses of reactants, the coefficients in the balanced chemical equation give the number of moles of each reactant needed and the number of moles of each product that can be produced. \( 26 .0\: \cancel{g\: Au} \times \dfrac{1\: \cancel{troy\: oz}} {31 .10\: \cancel{g}} \times \dfrac{\$1400} {1\: \cancel{troy\: oz\: Au}} = \$1170 \). Both the time of death and the chemical processes that take place after a person dies are of great interest to an investigator. If the sample from step 7 is not within 0.050 grams of the mass from step 6, heat again for a third time, cool and record the mass. Steps- 1) Put the constituents in water. Another conversion is needed at the end to report the final answer in tons. Show all work. One mole of carbonate ion will produce n moles of water. Weigh out approximately this amount of ascorbic acid directly into a 250-mL Erlenmeyer flask. To compare your results for the commercial product with those published on the label. This equation is not balanced because there are two oxygen atoms on the left side and only one on the right. { "01:_Introducing_Measurements_in_the_Laboratory_(Experiment)" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass228_0.
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