It is a compound containing potassium, oxygen, and chlorine. Name of Sample Used: ________________________________________________________. To balance equations that describe reactions in solution. the observed rate of decay depends on the amount of substance you have. 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. If an industrial plant must produce a certain number of tons of sulfuric acid per week, how much elemental sulfur must arrive by rail each week? Use the molar mass of CO2 (44.010 g/mol) to calculate the mass of CO2 corresponding to 1.51 mol of CO2: \[ mass\, of\, CO_2 = 1.51 \, mol \, CO_2 \times {44.010 \, g \, CO_2 \over 1 \, mol \, CO_2} = 66.5 \, g \, CO_2 \nonumber \]. Mass of crucible, lid + residue after 1st heating, Mass of crucible, lid + residue after 2nd heating, Mass of crucible, lid + residue after 3rd heating. Calculate the approximate mass of ascorbic acid you will need and have your instructor initial your calculations on the data sheet. To illustrate this procedure, consider the combustion of glucose. (Remember that you should generally carry extra significant digits through a multistep calculation to the end to avoid this!) Only if you know the approximate end-point of a titration should you add titrant faster, but when you come within a few milliliters of the endpoint you should begin to slow down and add titrant dropwise. Forward reaction: 2I- + 2H+ It is also called sodium hyposulfite or "hypo". This should be enough \(\ce{KIO3}\) for your group for. Note that the weight of your sample is expected to decrease by at least 30 % of its original mass (~ 0.3 g). With juices it sometimes takes a little longer for the blue color to fade, in which case the endpoint is where the color is permanent. Example #2: A hydrate of Na 2 CO 3 has a mass of 4.31 g before heating. Your final calculated results for each trial of this experiment should differ by less than 0.0005 M. Any trials outside this range should be repeated. Glucose reacts with oxygen to produce carbon dioxide and water: \[ C_6H_{12}O_6 (s) + 6 O_2 (g) \rightarrow 6 CO_2 (g) + 6 H_2O (l) \label{3.6.1} \]. Manufacturers claim: ____________________________ (value and units), Serving Size (if applicable): ________________________ (value and units). Be careful to only select products where the actual vitamin C content in mg or percent of RDA (recommended daily allowance) is listed. To do this, you will need three test tubes. In 1934, Rechstein worked out a simple, inexpensive, four-step process for synthesizing ascorbic acid from glucose. Copper only The copper (11) sulfate compound ONLY Score: 0/3 Submit Answer 4/4 submissions remaining 7. Explain your choice. Two moles of HCl react for every one mole of carbonate. 4.6 The rate and extent of chemical change. Show all your calculations on the back of this sheet. If you use a funnel to fill the burets be sure it is cleaned and rinsed in the same way as the burets and removed from the buret before you make any readings to avoid dripping from the funnel into the buret. A sample of NaClO3 is converted by heat to NaCl with a loss of 0.16 g of oxygen. There has been much controversy over speculation that Vitamin C intake should be much higher than the RDA for the prevention of colds and flu. 4.6.2 Reversible reactions and dynamic equilibruim Mix the two solutions and after a short delay, the clear . After heating, the mass of the anhydrous compound is found to be 3.22 g. Determine the formula of the hydrate and then write out the name of the hydrate. the equilibrium concentrations or pressures . Swirl to mix. Assume no heat loss to the calorimeter and assume the solution has a heat capacity of 4.18 J/0C.g. Elementary entities can be atoms, molecules, ions, or electrons. Begin your titration. Do not use another container to transfer the sample as any loss would result in a serious systematic error. In this experiment, a known mass of hydrated copper (II) sulfate is heated to remove the water of crystallisation. Powdered samples (such as drink mixes) may be used directly. - sodium chloride (NaCl) Remember that most items look exactly the same whether they are hot or cold. The formula is: C p = Q/mT. 3.2.4: Food- Let's Cook! A The equation is balanced as written; proceed to the stoichiometric calculation. To describe these numbers, we often use orders of magnitude. While adding the \(\ce{KIO3}\) swirl the flask to remove the color. These operations can be summarized as follows: \[ 45.3 \, g \, glucose \times {1 \, mol \, glucose \over 180.2 \, g \, glucose} \times {6 \, mol \, CO_2 \over 1 \, mol \, glucose} \times {44.010 \, g \, CO_2 \over 1 \, mol \, CO_2} = 66.4 \, g \, CO_2 \nonumber \]. When the vitamin C (ascorbic acid) is completely oxidized, the iodine, \(\ce{I2}\) (aq), will begin to build up and will react with the iodide ions, \(\ce{I^-}\) (aq), already present to form a highly colored blue \(\ce{I3^-}\)-starch complex, indicating the endpoint of our titration. The mixture is heated until the substance fully sublimates. The number of moles of CO2 produced is thus, \[ moles \, CO_2 = mol \, glucose \times {6 \, mol \, CO_2 \over 1 \, mol \, glucose } \nonumber \], \[ = 0.251 \, mol \, glucose \times {6 \, mol \, CO_2 \over 1 \, mol \, glucose } \nonumber \]. (ii) determine the formula of the hydrated compound. 6 days/2 days = 3 half lives 100/2 = 50 (1 half life) 50/2 = 25 (2 half lives) 25/2 = 12.5 (3 half lives) So 12.5g of the isotope would remain after 6 days. The space shuttle had to be designed to carry 0.126 tn of H2 for each 1.00 tn of O2. This page titled 10: Vitamin C Analysis (Experiment) is shared under a CC BY-NC license and was authored, remixed, and/or curated by Santa Monica College. Remove any air bubbles from the tips. Refilling the buret in the middle of a trial introduces more error than is generally acceptable for analytical work. A 15.67 g hydrate sample of magnesium carbonate weighed in at 7.58 g after heating. You therefore decide to eat a candy bar to make sure that your brain does not run out of energy during the exam (even though there is no direct evidence that consumption of candy bars improves performance on chemistry exams). The problem asks for the mass of gold that can be obtained, so the number of moles of gold must be converted to the corresponding mass using the molar mass of gold: \( \begin{align} mass\: of\: Au &= (moles\: Au)(molar\: mass\: Au) \\ Redox titration using sodium thiosulphate is also known as iodometric titration. Avoid contact with iodine solutions, as they will stain your skin. 2KIO 3 2KI + 3O 2. Given 100 g of cinnabar, how much elemental mercury can be produced from this reaction? However, some 400 years were to pass before Vitamin C was isolated, characterized, and synthesized. Solution: 1) Determine mass of water driven off: 4.31 3.22 = 1.09 g of water. Record the mass added in each trial to three decimal places in your data table. Calculate the number of mg of Vitamin C per serving. Calculate milligrams of ascorbic acid per gram of sample. (The answer determines whether the ore deposit is worth mining.) A stoichiometric quantity is the amount of product or reactant specified by the coefficients in a balanced chemical equation. Clean and rinse a large 600-mL beaker using deionized water. KMnO 4 + HCl = KCl + MnCl 2 + H 2 O + Cl 2. As shown in the figure and photo on the following page, place your clay triangle on the ring, and then place the crucible containing the sample onto the triangle. Question #fee47 Question #c5c15 Question #19eb9 Question #e2ea2 Question #bc751 Question #e2ea6 . How long must the sample be heated the first time (total)? We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. in aqueous solutions it would be: 50 mL of distilled water. Quantitative calculations that involve the stoichiometry of reactions in solution use volumes of solutions of known concentration instead of masses of reactants or products. The large cylinder in the middle contains the oxygen and hydrogen that fueled the shuttles main engine. Solid potassium chlorate (\(\ce{KClO3}\)), solid potassium chloride (\(\ce{KCl}\)), 6M nitric acid (\(\ce{HNO3}\)), 0.1M silver nitrate (\(\ce{AgNO3}\)), two crucibles with lids, stand and ring clamp, clay triangle, crucible tongs, Bunsen burner, three medium-sized test tubes, test tube rack, stirring rod, and an electronic balance. Explain how your observations in the table above verify that the residue in your crucible after heating is potassium chloride. The balanced chemical equation for the reaction and either the masses of solid reactants and products or the volumes of solutions of reactants and products can be used to determine the amounts of other species, as illustrated in the following examples. Discrepancies between the two values are attributed to rounding errors resulting from using stepwise calculations in steps 13. Add titrant from the buret dropwise, swirling between drops to determine if a color change has occurred. The specific gravity of Potassium iodate. Weigh out enough powdered sample, so that there will be about 100 mg of ascorbic acid (according to the percentage of the RDA or mg/serving listed by the manufacturer) in each trial. Once the supply of HSO3- is exhausted, I3- persists in . To calculate the mass of gold recovered, multiply the number of moles of gold by its molar mass. Was your average experimental mass percent of oxygen in potassium chlorate higher or lower than the theoretical value (circle one)? 2) Filter the soln. You will have to heat your sample of potassium chlorate at least twice. These items are now known to be good sources of ascorbic acid. CHEM1405 Answers to Problem Sheet 1 1. liquid mercury element ice molecular compound neon gas element liquid nitrogen element milk mixture copper pipe element Another conversion is needed at the end to report the final answer in tons. Alchemists produced elemental mercury by roasting cinnabar ore in air: \[ HgS (s) + O_2 (g) \rightarrow Hg (l) + SO_2 (g) \nonumber \]. Now heat the sample a second time for an additional 6 minutes using a high temperature flame. Show all work. While adding the \(\ce{KIO3}\) swirl the flask to remove the color. What does the chemical formula KIO3 plus H2O plus Na2S2O5 produce? Calculate how many tons of hydrogen a space shuttle needed to carry for each 1.00 tn of oxygen (1 tn = 2000 lb). 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. It is recommended that pregnant women consume an additional 20 mg/day. 5) Mass of hydrated salt mass of anhydrous salt = mass of water. (you will need this calculation to start the lab). 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). How many grams of pure gold can be obtained from a ton of low-grade gold ore? WASTE DISPOSAL: You may pour the blue colored titrated solutions into the sink. To analyze an unknown and commercial product for vitamin C content via titration. If a spill of either chemical occurs, rinse under running water and report the accident to your instructor. Which of the following sources of error could be used to explain this discrepancy (circle one)? Potassium Chlorate is an inorganic compound with the chemical formula KClO 3. NH4N03 is added to the water in the calorimeter. Do you expect it weigh more than, less than or the same as the original potassium chlorate sample? 7) Determine smallest whole-number ratio between sodium carbonate and water: Calculate empirical formula when given mass data, Calculate empirical formula when given percent composition data, Determine identity of an element from a binary formula and a percent composition, Determine identity of an element from a binary formula and mass data. How long must the sample be heated the second time? These solids are all dissolved in distilled water. Because of its mercury content, cinnabar can be toxic to human beings; however, because of its red color, it has also been used since ancient times as a pigment. Clean both crucibles and their lids (obtained from the stockroom) by thoroughly rinsing with distilled water then drying as completely as possible with a paper towel. For example, if a substance reacts with the oxygen in air, then oxygen is in obvious (but unstated) excess. We need to know two things in order to calculate the numeric value of the equilibrium constant: the balanced equation for the reaction system, including the physical states of each species. Specifically, the residue will be tested for the presence of chloride ions by the addition of nitric acid and aqueous silver nitrate. Be sure the product you select actually contains vitamin C (as listed on the label or in a text or website) and be sure to save the label or reference for comparison to your final results. Finally, convert the mass of H2 to the desired units (tons) by using the appropriate conversion factors: \[ tons \, H_2 = 1.14 \times 10^5 \, g \, H_2 \times {1 \, lb \over 453.6 \, g} \times {1 \, tn \over 2000 \, lb} = 0.126 \, tn \, H_2 \nonumber \].
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