Sodium Thiosulfate Reaction

eLearning 2009 Publication No. 91860 set of reply of Sodium Thiosulfate and Hydrochloric sultry Rate Laws Introduction The purpose of this presentation is to investigate the effect of atomic number 11 thiosulfate intentness on the appreciate of answer of sodium thiosulfate with hydrochloric point. The chemic chemical reception, which produces warm sulfur, will be followed by measuring the conviction needed for the reaction mixture to become opaque. The results will be study graphically to determine the order of reaction the mathematical relationship betwixt the reactant stringency and the rate.Concepts Kinetics Order of reaction Rate law density existents Hydrochloric acrid ancestor, HCl, 2 M, 25 mL Sodium thiosulfate solution, Na2S2O3, 0. 15 M, one hundred fifty mL Distilled or deionized water Beakers, 100-mL, 5 graduated cylinders, 50- or 100-mL, 2 Graduated cylinders, 10-mL, 5 Overhead projector or light concussion ineradicable marker tizzyring rods S topwatch or successionr Safety Precautions Hydrochloric acid solution is corrosive to look and skin. It is moderately toxic by use of goods and services and inhalation. Sodium thiosulfate solution is a body tissue irritant.The reaction of sodium thiosulfate and hydrochloric acid generates sulfur dioxide gas, which is a skin and eye irritant. Perform this display in a well-ventilated lab only. Avoid contact of all chemicals with eyes and skin. Wear chemical splash goggles, temperature-resistant gloves, and chemical-resistant apron. Please review menses Material Safety entropy Sheets for additional safety, handling, and governing body information. Procedure 1. Label five dollar bill 100-mL beakers 15 and clean the bottom of to each one beaker. 2. Draw a large X across the bottom on the outside of each beaker.Place the beakers on an overhead projector stage or a light box so that scholars can view the X. 3. Using secernate graduated cylinders for the solution and water, mea sure and add the required amounts of 0. 15 M sodium thiosulfate and distilled water to each beaker. Be as precise as possible. Beaker 0. 15 M Na2S2O3 Distilled Water 1 50. 0 mL 0 mL 2 40. 0 mL 10. 0 mL 3 30. 0 mL 20. 0 mL 4 20. 0 mL 30. 0 mL 5 10. 0 mL 40. 0 mL 4. Have students cypher the final concentration of sodium thiosulfate in each beaker 15. 91860 011509 Flinn scientific commandment Chemistry eLearning word-painting Series 5. eternize the following information in a data table Beaker, volume of Na2S2O3 solution, volume of distilled water, concentration of Na2S2O3, reaction prison term (sec), and 1/reaction snip (reaction rate). See the Sample selective information and Results table in the treatment section. 6. Measure 5. 0 mL of 2 M hydrochloric acid into each of five 10-mL graduated cylinders. 7. Starting with beaker 1, guardedly add the HCl all in one pour to the sodium thiosulfate solution. Stir the solution once with a stirring rod and immediately shekels timing. 8. Stop timing when the black X is no longer visible. Record the reaction time in seconds in the data table. . Repeat steps 7 and 8 with beakers 25. 10. Calculate 1/reaction time for each trial. Plot concentration vs. time and concentration vs. 1/time on separate graphs. presidential term Please consult your current Flinn scientific Catalog/Reference Manual for general guidelines and specific procedures governing the disposal of laboratory waste. Collect the leftover reaction mixtures and filter to separate the solid sulfur product. The sulfur may be disposed of in a landfill according to Flinn Suggested Disposal Method 26a. The filtrate may be neutralized and disposed of down the drain with excess water according toFlinn Suggested Disposal Method 26b. Tips This natural action may be performed as a chemical demonstration with classroom participation or as a student activity. The contents of the beakers project well on an overhead projector and the time to the slice of the black X is easily seen and measured. The reaction may be downsized for a student lab activity. Carry out individual trials in separate wells in a 6-well reaction plate or in small medicine cups. If students will be doing the experiment in the lab, it is a good idea for them to start with beaker 5, because it takes the longest time. The activity may overly be performed as a cooperative class exercise with antithetic groups investigating different variables, including the effect of HCl concentration and the effect of temperature. The reaction rate is zero-order with respect to HCl. Empty the beakers and clean them thoroughly using paper towels to mutilate the sulfur. If the colloidal sulfur is allowed to sit in the beakers for an extended time, it will be much more difficult to remove the deposits from the glass. To achieve better commingle of the reactants, add the hydrochloric acid using a 10-mL luer-lock plastic syringe (without needle).Squirt the acid using a fair amount of force. When lower concentrations of sodium thiosulfate ar used, the rate law does not appear to be as naive as predicted in this experiment. At lower concentrations, the reaction appears to be close at hand(predicate) to 3/2-order in sodium thiosulfate and 1/2-order in hydrochloric acid. The reaction time is more difficult to measure at lower concentrations because the onset of turbidity is more gradual. Both the overall chemical equation and the mechanism for the radioactive decay of sodium thiosulfate ar more complex than suggested by Equation 1.The reaction is acid-catalyzed, which means that the acid concentration must have some coach on the rate in terms of producing an equilibrium concentration of HS2O3 ions, The HS2O3 ion is a reactive intermediate, reacting further with additional S2O32 ions to produce polymeric ions containing multiple S atoms. When the chain of S atoms in a polymeric ion becomes long enough, it closes in on itself to form a ring of elemental sulfur (S8) . S2O32 + H+ HS2O3 HSSO3 + nS2O32 HS(S)nSO3 + nSO32 HSSnSO3 H+ + SSnSO3 SS7SO3 S8 + SO32 2 2009 Flinn Scientific, Inc. All Rights Reserved. 91860 Discussion Sodium thiosulfate reacts with hydrochloric acid to form sulfur and sulfur dioxide (Equation 1). Na2S2O3(aq) + 2HCl(aq) S(s) + SO2(g) + 2NaCl(aq) Equation 1 The kinetics of the reaction can be analyzed by graphing the concentration of Na2S2O3 as a function of both reaction time and 1/time. A plot of concentration versus time gives a curved line, which levels mop up as it approaches the x-axisthe reaction slows down as the reactant concentration decreases. The rate of a reaction is inversely proportional to reaction time.A plot of concentration of versus 1/time gives a straight line. The rate is directly proportional to concentration, and the reaction appears to be first order with respect to sodium thiosulfate concentration. Sample Data and Results Beaker 1 2 3 4 5 Volume of Na2S2O3 (mL) 50 40 30 20 10 Volum e of H2O (mL) 0 10 20 30 40 Na2S2O3, M 0. 15 0. 12 0. 090 0. 060 0. 030 Reaction time (sec) 22. 5 27. 3 35. 1 60. 0 159. 1 Reaction rate (1/time, sec1) . 0444 . 0367 . 0285 . 0167 . 00629 180 160 140 long hundred 100 80 60 40 20 0 0. 00 onus of concentration on reaction time 0. 05 0. 10 0. 15 0. 20 Na 2 S2 O3 Concentration, M 0. 07 0. 6 0. 05 0. 04 0. 03 0. 02 0. 01 0 0. 00 Effect of concentration on reaction rate 0. 05 Na 2 S2 O3 Concentration, M 0. 10 0. 15 0. 20 3 2009 Flinn Scientific, Inc. All Rights Reserved. 91860 Connecting to the National archetypes This laboratory activity relates to the following National Science Education Standards (1996) Unifying Concepts and Processes Grades K12 Evidence, models, and explanation Constancy, change, and measurement Content Standards Grades 912 Content Standard A Science as Inquiry Content Standard B Physical Science, structure and properties of matter, chemical reactions, motions and forcesFlinn ScientificTeaching Chemistry eLearning Video Series A video of the Rate of Reaction of Sodium Thiosulfate and Hydrochloric Acid activity, presented by Annis Hapkiewicz, is useable in Rate Laws, part of the Flinn ScientificTeaching Chemistry eLearning Video Series. Materials for Rate of Reaction of Sodium Thiosulfate and Hydrochloric Acid are available from Flinn Scientific, Inc. Materials required to perform this activity are available in the Reaction Order and Rate LawsStudent Laboratory Kit available from Flinn Scientific.Materials may also be purchased separately. Catalog No. Description AP4864 H0034 S0114 AP1572 GP1010 GP2005 GP2015 Reaction Order and Rate LawsStudent Laboratory Kit Hydrochloric Acid, 3 M, ergocalciferol mL Sodium Thiosulfate Pentahydrate, Reagent, 500 g Timer, Stopwatch, Flinn Beaker, Borosilicate Glass, 100 mL Graduated Cylinder, Borosilicate Glass, 10-mL Graduated Cylinder, Borosilicate Glass, 50-mL Consult your Flinn Scientific Catalog/Reference Manual for current prices. 4 2009 Flinn Scientific , Inc. All Rights Reserved. 91860