Methylbromide, CH 3 Br , is used in agriculture to fumigate soil to rid it of pests such as nematodes. It is injected directly into the soil, but over time it has a tendency to escape before it can undergo natural degradation to innocuous products. Soil chemists have found that ammonium thiosulfate, ( NH 4 ) 2 S 2 O 3 , a nitrogen and sulfur fertilizer, drastically reduces methylbromide emissions by causing it to degrade. In a chemical analysis to determine the purity of a batch of commercial ammonium thiosulfate, a chemist first prepared a standard solution of iodine following the procedure in Problem 5.91. First, 0.462 g KlO 3 was dissolved in water to make 125 mL of solution. The solution was made acidic and treated with excess potassium iodide, which caused the following reaction to take place: IO 3 - +8I - +6H + → 3I 3 - +3H 2 O The solution containing the I 3 - ion was then diluted to exactly 250.0 mL in a volumetric flask. Next, the chemist dissolved 0.2180 g of the fertilizer in water, added starch indicator, and titrated it with the standard I 3 - solution. The reaction was 2 S 2 O 3 2 − + I - 3 → S 4 O 6 2 − + 3 I - The titration required 27.99 mL of the I 3 - solution. (a) What was the molarity of the I 3 - solution used in the titration? (b) How many grams of ( NH 4 ) 2 S 2 O 3 were in the fertilizer sample? (c) What was the percentage by mass of ( NH 4 ) 2 S 2 O 3 in the fertilizer?
Methylbromide, CH 3 Br , is used in agriculture to fumigate soil to rid it of pests such as nematodes. It is injected directly into the soil, but over time it has a tendency to escape before it can undergo natural degradation to innocuous products. Soil chemists have found that ammonium thiosulfate, ( NH 4 ) 2 S 2 O 3 , a nitrogen and sulfur fertilizer, drastically reduces methylbromide emissions by causing it to degrade. In a chemical analysis to determine the purity of a batch of commercial ammonium thiosulfate, a chemist first prepared a standard solution of iodine following the procedure in Problem 5.91. First, 0.462 g KlO 3 was dissolved in water to make 125 mL of solution. The solution was made acidic and treated with excess potassium iodide, which caused the following reaction to take place: IO 3 - +8I - +6H + → 3I 3 - +3H 2 O The solution containing the I 3 - ion was then diluted to exactly 250.0 mL in a volumetric flask. Next, the chemist dissolved 0.2180 g of the fertilizer in water, added starch indicator, and titrated it with the standard I 3 - solution. The reaction was 2 S 2 O 3 2 − + I - 3 → S 4 O 6 2 − + 3 I - The titration required 27.99 mL of the I 3 - solution. (a) What was the molarity of the I 3 - solution used in the titration? (b) How many grams of ( NH 4 ) 2 S 2 O 3 were in the fertilizer sample? (c) What was the percentage by mass of ( NH 4 ) 2 S 2 O 3 in the fertilizer?
Methylbromide,
CH
3
Br
, is used in agriculture to fumigate soil to rid it of pests such as nematodes. It is injected directly into the soil, but over time it has a tendency to escape before it can undergo natural degradation to innocuous products. Soil chemists have found that ammonium thiosulfate,
(
NH
4
)
2
S
2
O
3
, a nitrogen and sulfur fertilizer, drastically reduces methylbromide emissions by causing it to degrade. In a chemical analysis to determine the purity of a batch of commercial ammonium thiosulfate, a chemist first prepared a standard solution of iodine following the procedure in Problem 5.91. First, 0.462 g
KlO
3
was dissolved in water to make 125 mL of solution. The solution was made acidic and treated with excess potassium iodide, which caused the following reaction to take place:
IO
3
-
+8I
-
+6H
+
→
3I
3
-
+3H
2
O
The solution containing the
I
3
-
ion was then diluted to exactly 250.0 mL in a volumetric flask. Next, the chemist dissolved 0.2180 g of the fertilizer in water, added starch indicator, and titrated it with the standard
I
3
-
solution. The reaction was
2
S
2
O
3
2
−
+
I
-
3
→
S
4
O
6
2
−
+
3
I
-
The titration required 27.99 mL of the
I
3
-
solution.
(a) What was the molarity of the
I
3
-
solution used in the titration?
(b) How many grams of
(
NH
4
)
2
S
2
O
3
were in the fertilizer sample?
(c) What was the percentage by mass of
(
NH
4
)
2
S
2
O
3
in the fertilizer?
#1. Retro-Electrochemical Reaction: A ring has been made, but the light is causing the molecule to un-
cyclize. Undo the ring into all possible molecules. (2pts, no partial credit)
hv
Chemistry: An Introduction to General, Organic, and Biological Chemistry (13th Edition)
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