Suppose a student needs to standardize a sodium thiosulfate, Na2S2O3,Na2S2O3, solution for a titration experiment. To do so, he or she will react it with a solution of iodine. The student adds a 1.00 mL1.00 mL aliquot of 0.0200 M KIO30.0200 M KIO3 solution to a flask, followed by 3 mL3 mL of distilled water, 0.2 g0.2 g of solid KI, KI, and 1 mL H2SO4.1 mL H2SO4. The student then titrates the solution with sodium thiosulfate solution in order to determine the exact concentration of Na2S2O3.Na2S2O3. The end point of the titration is reached after 0.90 mL0.90 mL of Na2S2O3Na2S2O3 is dispensed from a microburet. What is the concentration of the standard sodium thiosulfate solution?

The concentration of the standard sodium thiosulfate solution is ; 0.133

The net chemical reaction equation

IO₃⁻  +  6H⁺  +   6S₂O₃³⁻ >  I⁻  +  3S₄O₆²⁻  + 3H₂O

First step : Determine the moles of  KIO₃

number of moles = molarity * volume

                            = 0.02 mol / L * 0.01 L

                            = 0.00002 mol

From the net chemical reaction equation

one ( 1 ) mole of KIO₃ reacts with 6 moles of S₂O₃²⁻

∴ number of moles in the reaction = 6 * 0.00002 = 0.00012 mol.

Final step : Determine the concentration of sodium thiosulfate solution

Given Volume = 0.90 ml = 0.0009 L

∴ concentration of sodium thiosulfate solution

   =  0.00012 / 0.0009  =  0.133

Hence we can conclude that The concentration of the standard sodium thiosulfate solution is ; 0.133

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0.133

Explanation:

reaction between KIO3 and KI in acidic medium

IO3⁻ +5I⁻ +6h⁺ → 3I₂ + 3H₂O

I₂ reacts with thiosulphate

NaS₂O₃  → 2Na⁺ + S₂O₃²⁻

net reaction

IO⁻₃ + 6H⁺ + 6S₂O₃³⁻ → I⁻ + 3S₄O₆²⁻ + 3H₂O

mole of KIO₃

= molarity x volume

= 0.00002mol

a mole of KIO₃ has reaction with 6 mol of S₂O₃²⁻

= 2x6x10⁻⁵

= 0.00012 mol

volume = 0.90 ml

1 ml = 0.001L

0.90ML  = 0.0009L

to get concentration,

molarity/volume

= 0.00012/0.0009

= 0.133m

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a rain shadow is a dry region of land on the side that is protected against the prevailing winds of a mountain range. the prevailing winds are the winds that occur most of the time in a particular place of the earth

prevailing winds carry air toward the mountain range. as the air rises up over a mountain range, the air cools, water vapor condenses, and clouds form. on this side of the mountains, called the windward side, precipitation falls in the form of  rain  or snow. this dry air produces a  rain shadow.