S. Generation of oxides of nitrogen (NOx and sulfur (SOx) (Acid Rain) 3.1 Place
ID: 1068336 • Letter: S
Question
S. Generation of oxides of nitrogen (NOx and sulfur (SOx) (Acid Rain) 3.1 Place the Petrie dish on one of the circles containing a grid. Note that this will give you a grid in order to place drops at specific distances relative to the center. Place one drop of bromocresol green indicator (blue or green form) at each line around the center (three total) at 12:00 and 6:00 if looking at template like a clock face. Repeat this using Methyl Red as an indicator (yellow form) at 3:00 and 9:00 respectively. Place a mixture containing one drop each of KI and starch on the outside line at 1:00 and 7:00. (See Figure I below) 3.2 Place 1-2 drops of 0.5M potassium nitrite (KNOh, or the corresponding sodium salt NaNO) in the center of the Petrie dish followed by 2-3 drops of 1M sulfuric acid. Cover the Petrie dish and record any changes you observed. Remember you have two indicators present as well as KI/starch solution.Explanation / Answer
Reaction -
Nox+H2SO4 +dye =redox reaction
KNO2+H2SO4--->NOx +[O](acid) [strong oxidising agent] as N is in higher oxidation state capable of getting to lower states(reduced)
1) fast reaction as the green changed to yellow and then brown irrespective of the distance from the centre where Nox+H2SO4 was placed that produced bubbles of gas NOx to react with the dye(oxidizing agent)
2)Red methyl -no reaction
3)KI+starch -very fast reaction as the reaction happened when it was placed distant from the centre.
Na2SO3+ H2SO4 +dye
Na2SO3+H2SO4---->SO2+Na2SO4+H2O
1)Red methyl -slow reaction ,drops closer reacted sooner than the distant drops
2)green indicator -fast reaction
SOx does not react with KI and starch as it is weak reducing agent for KI
HCl + Na2SO3---->NaCl +SO2+H2O similar reaction as with H2SO4 but HCl does not give Nox with KNo2
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