Chemistry Molarity standardization of thiosulfate/titration of hypochlorite?
This is a redox volumetry, so it's helpful to start by writing the hemi-reactions involved. S2O3 2- will be oxidized to S4O6 2-. That's from S(II) to S(II 1/2) , so we balance with electrons in basic medium: 2 S2O3 2- => S4O6 2- + 2 e - IO3 - will be reduced to I -. Again, that would be from I(V) to I(-I), and we write: IO3 - + 3 H2O + 6 e - => I - + 6 OH - Finally, ClO - will be reduced to Cl -, which is from Cl(I) to Cl(-I), yielding: ClO - + H2O + 2 e - => Cl - + 2 OH - So: a mole of S2O3 2- is worth a mole of electrons, while a mole of IO3 - and a mole of ClO - are worth 6 moles and 2 moles of electrons respectively. The reaction first reaction (standarization of the NaS2O3 solution) is: 6 S2O3 2- + IO3 - + 3 H2O => 3 S4O6 2- + I - + 6 OH - so: Volume of KIO3 * Molarity of KIO3 * 6 = Volume of NaS2O3 * Molarity of NaS2O3 Either use a standarized KIO3 solution or make your own using an analytical (+/- 0.0001g) scale and a volumetric flask. The only unknown on that equation should be the molarity of the NaS2O3 solution: Molarity of NaS2O3 = 6 * Volume of KIO3 * Molarity of KIO3 / Volume of NaS2O3 Now, for the bleach: You speak of diluted and undiluted, but never of the dilution factor, so I'll work on the general case: You take a volume Vb of bleach which you dilute with water in a volumetric flask to a final volume of Vf, and then proceed to titrate this diluted solution. The reaction is: 2 S2O3 2- + ClO - + H2O => S4O6 2- + Cl - + 2 OH - so: Volume of NaClO * Molarity of NaClO * 2 = Volume of NaS2O3 * Molarity of NaS2O3 The only unknown now is the molarity of the diluted bleach: Molarity of NaClO = Volume of NaS2O3 * Molarity of NaS2O3 / 2 * Volume of NaClO Now: Molarity of undiluted bleach = Molarity of diluted bleach * Vf / Vb And finaly: Molarity of undiluted bleach * Mr(NaClO) / 10 * Density of undiluted bleach = grams of NaClO / 100 grams of undliuted bleach = % NaOCl (m/m) in undiluted bleach. I supose the density can be assumed to be water's.
A .15 g sample of kio3 required 10.6 mL of Na2S2O3 solution for its standardization. what is the molarity of t?
Supposing the reactions to be: IO3{-} + 5 I{-} + 6 H{+} → 3 I2 + 3 H2O 2 S2O3{2-} + I2 → S4O6{2-} + 2 I{-} (0.15 g KIO3) / (214.001 g KIO3/mol) x (3 mol I2 / 1 mol KIO3) x (2 mol S2O3{2-} / 1 mol I2) / (0.0106 L) = 0.40 mol/L Na2S2O3
What is the difference between primary and secondary standard substance?
Definition of StandardsStandards are materials containing a precisely known concentration of a substance for use in quantitative analysis.A standard provides a reference that can be used to determine unknown concentrations or to calibrate analytical instruments.Primary StandardsA primary standard is a reagent that is extremely pure, stable, it not a hydrate/has no water of hydration, and has a high molecular weight.Examples of primary standards for titration of acids are:>> sodium carbonate: Na2CO3, mol wt. = 105.99 g/mol >> tris-(hydroxymethyl)aminomethane (TRIS or THAM): (CH2OH)3CNH2, mol wt. = 121.14 g/molExamples of primary standards for titration of bases are:>> potassium hydrogen phthalate (KHP): KHC8H4O4, mol wt. = 204.23 g/mol >> potassium hydrogen iodate: KH(IO3)2, mol wt. = 389.92 g/molExamples of primary standards for redox titrations are:>> potassium dichromate: K2Cr2O7, mol wt. = 294.19 g/mol >> sodium oxalate: Na2C2O4 mol wt. = 134.00 g/molSecondary StandardsA secondary standard is a standard that is prepared in the laboratory for a specific analysis.It is usually standardized against a primary standard.NIST Standard Reference MaterialsThe National Institute of Standards and Technology (NIST) provides a wide variety of standard reference materials (SRMs) for validating and calibrating analytical methods. Some examples of SRMs are:1. For chemical composition elements in iron, steels, and other metal alloys sulfur in fossil fuels polychlorinated biphenyls (PCBs) in oils elements in foods and beverages (e.g. milk powder, wheat flour)2. For physical properties strength and melt fow of polyethylene pipe radioactivity electrical resistivity of silicon3. For engineering materials particle sizes magnetic computer storage media surface flammability
How are “n-factor” in a reaction calculated?
Hypo solution (sodium thiosulfate, Na2S2O3.5H2O) is a good reductant.With iodine, l2, it gives (S4O6)2-, tetra-thionate. I2 + 2Na2S2O3 = Na2S4O6 + 2NaIHere, oxidation number per sulphur atom changes from +2 to +2.5.But, one thiosulfate ion has two sulphur atoms, hence, n-factor i.e., total change in oxidation number per molecule is 0.5 x 2 = 1.Sodium thiosulfate, Na2S2O3.5H2O, when reacts with stronger oxidant Cl2 or Br2, it is oxidised to greater extent and gives (SO4)2-, sulfate.Na2S2O3 + 4 Cl2 + 5 H2O → 2 NaHSO4 + 8 HCl Here, oxidation number per sulphur atom changes from +2 to +6.But, one thiosulfate ion has two sulphur atoms, hence, n-factor i.e., total change in oxidation number per molecule/ion is 4 x 2 = 8.For Redox reactions, n-factor = total number of electrons being exchanged by one molecule/ion of given substance in the reaction or, n-factor = total “exchange” in oxidation state by different elements of one molecule/ion of given substance in the reactione.g,Oxalate ion acts as reductant and gives CO2. Here, oxidation number per carbon atom changes from +3 to +4. But, since one oxalate ion has two carbon atoms, hence, total change in oxidation number is 2 x 1 = 2.Dichromate ion acts as oxidant and gives green, Cr3+. Here, oxidation number per chromium atom changes from +3 to +6. But, since one dichromate ion has two chromium atoms, hence, hence, n-factor i.e., total change in oxidation number per molecule is 3 x 2 =6.
How do I calculate my molarity of Na2S2O3 solution?
I have my grams of KIO3, but how am I supposed to go from there to moles of Na2S2O3? My moles of IO3 is 1.56x10E-3 and I put that in .025L of my solution if that matters. I'm just really confused and could use all the help I can get. Thanks!
What is the number of moles of S2O3^(2-) in 0.01L of a solution of 0.01mol/L of Na2S2O3?
“What is the number of moles of S2O3^(2-) in 0.01L of a solution of 0.01mol/L of Na2S2O3?”Well, you have a .01M solution of Sodium Thiosulfate. So, based on the formula, Na2S2O3, in 1 mole of sodium thiosulfate there are 2 moles of Na + ions, and 1 mole of S2O3 2- ions, therefore the ratio of S2O3/Na2S2O3 is 1:1. So if you had a 1M solution of Sodium Thiosulfate, you'd have 1 mole of Thiosulfate ions in solution.Back to the problem;So, now we've determined that your solution has .01mol/L of Thiosulfate ions, same as the molarity of the solution, so now we use the definition of molarity to find the absolute number of moles. So we take .01mol/L • .01L and that gives us the number of moles in solution, which is .0001mol of Na2S2O3.
Chemistry Question - Finding Moles and Concentration?
A solution of sodium thiosulfate (Na2S2O3) was standardized against potassium iodate (KIO3). A known mass of KIO3 was titrated with Na2S2O3 solution until the blue color disappeared after the addition of starch solution. KIO3 + 5KI + 6Na2S2O3 + 3H2SO4 3 H2O + 3K2SO4 + 6NaI + 3Na2S4O6 Mass of KIO3 used for standardization (g): 0.2164 Volume of Na2S2O3 required for titration (mL): 6.20 Using the volume of Na2S2O3 used for titration, calculate the following: What is the Molecular Weight of potassium iodate (KIO3) in g/mol? How many moles of KIO3 were used in the standardization of the Na2S2O3 solution? How many moles of Na2S2O3 were used? Calculate the concentration of Na2S2O3 solution in (mol/L). I really only need help with the last two - thanks in advance!!!
Molar concentration, net ionic helpppp?
1.a 25.0 ml volume of 0.0106M KIO3 is pipetted into a 250ml erlenmeyer flask. the solution is titrated to the stoichiometric point with 16.25ml of a sodium thiosulfate solution. what is the molar concentration of the sodium thiosulfate solution? 2.write the net ionic equation for the analysis of the "available chlorine" in a sample using sodium thiosulfate as the reducing agent by combining these 3 equations CL2(aq) + 2 OH-(aq) -----> CLO-(aq) + CL-(aq) + H2O(l) ClO-(aq) + 3I-(aq) + H2O (l) --> I3-(aq) + Cl-(aq) + 2OH-(aq) I3-(aq) + 2S2O32-(aq) --> 3I-(aq, colourless) + S4O62-(aq) 3. a 10.0 ml volume of "ultra bleach" is diluted to 100 ml in a volumetric flask. a 250 ml sample of this solution is analyzed according to the procedure in this experiment. given that 31.6 ml of 0.141 M Na2S2O3 is needed to reach the stoichiometric point, answer the following a. how many grams of "available" cl2 are in the titrated sample? b. how many grams of "ultra bleach" bleach solution are analyzed? assume the density of bleach is 1.084 g/ml c. calculate the percent " available chlorine" in the "ultra bleach" pleaseeee helppp
Concentration of Vitamin C problem?
The name vitamin C always refers to the L-enantiomer of ascorbic acid and its oxidized forms. The opposite D-enantiomer called D-ascorbate has equal antioxidant power, but is not found in nature, and has no physiological significance. When D-ascorbate is synthesized and given to animals that require vitamin C in the diet, it has been found to have far less vitamin activity than the L-enantiomer. Therefore, unless written otherwise, "ascorbate" and "ascorbic acid" refer in the nutritional literature to L-ascorbate and L-ascorbic acid respectively. This notation will be followed in this article. Similarly, their oxidized derivatives (dehydroascorbate, etc., see below) are all L-enantiomers, and also need not be written with full sterochemical notation here. Ascorbic acid is a weak sugar acid structurally related to glucose. In biological systems, ascorbic acid can be found only at low pH, but in neutral solutions above pH 5 is predominantly found in the ionized form, ascorbate. All of these molecules have vitamin C activity, therefore, and are used synonymously with vitamin C, unless otherwise specified.
Concentration of Vitamin C problem?
Concentration of Vitamin C problem? A) How many moles of I3^- are produced from the reaction between KI, H2SO4 and KIO3? B)Calculate how many moles of I3^- are consumed from the reaction with thiosumfate in each titration? C)Calculate the concentration in moles per liter of Vitamin C? Given the Following: -It took 20.477mL of Na2S2O3(thiosulfate) to standardize the unknown solution -25.00 ml of KIO3 was used -25.00 ml of the unknown solution was used P.S If you don't want to answer the problems please just explain how I would go about solving them because I have no idea as to how to solve these problems. Also the concentration of the KIO3 was 0.0200 M and the Na2S2O3 concentration was 0.079857322 M