How to Detect Phosphorus, Metal, and Oxygen in Organic Compounds | Chemistry Class 11

TL;DR

Phosphorus in an organic compound can be estimated by either the ammonium molybdate method or the magnesium method. In the first method, phosphorus is converted to phosphoric acid and then precipitated as ammonium phosphor molybdate, whose molar mass is 1,877 grams per mole. The second method ultimately produces magnesium pyrophosphate. Read on for the reaction steps, precipitates, and calculation relationships used in both methods.

Transcript

click the bell icon to get latest videos from equator health it's in the previous section we have understood that how can we determine or how can we estimate the percentage of nitrogen carbon hydrogen or various other elements that could be present in the organic component and now in this topic basically we are going to discuss about that how can w... Read More

Key Insights

• ❓ Two methods, using ammonium molybdate and magnesium, can be used to estimate the percentage of phosphorus in organic compounds.
• 🪜 The ammonium molybdate method involves a series of steps, including treating the organic compound with fuming nitric acid and adding ammonia and ammonium molybdate.
• 🪜 The magnesium method requires reacting the organic compound with fuming nitric acid and adding magnesia.
• ❓ The products obtained in both methods, ammonium phosphor molybdate and magnesium pyrophosphate, are used to calculate the percentage of phosphorus.
• 🖐️ The molar masses of the precipitates play a crucial role in the calculations.
• ❓ The percentage of phosphorus can be determined by substituting the values into the respective formulas.

Questions & Answers

Q: What are the two methods for estimating phosphorus in an organic compound?

The two methods use ammonium molybdate and magnesium. Both produce a phosphorus-containing product whose mass can be used to estimate the amount of phosphorus in the original organic compound.

Q: How does the ammonium molybdate method estimate phosphorus?

The organic compound is first treated with fuming nitric acid. If phosphorus is present, phosphoric acid forms; ammonia and ammonium molybdate are then added to produce an ammonium phosphor molybdate precipitate.

Q: Why is fuming nitric acid used in phosphorus estimation?

Fuming nitric acid reacts with the phosphorus-containing organic compound and forms phosphoric acid through oxidation. This phosphoric acid is then used in the subsequent precipitation steps.

Q: What precipitate forms in the ammonium molybdate method?

Adding ammonia and ammonium molybdate to phosphoric acid forms ammonium phosphor molybdate. This precipitate is the product used to estimate the phosphorus content.

Q: What is the molar mass of ammonium phosphor molybdate?

The stated molar mass of ammonium phosphor molybdate is 1,877 grams per mole. According to the calculation relationship, 1,877 grams of this precipitate contains 31 grams of phosphorus.

Q: How is the mass of phosphorus calculated from ammonium phosphor molybdate?

If the obtained precipitate has a mass of M1 grams, its phosphorus mass is calculated as 31 × M1 ÷ 1,877 grams. This relationship follows from 1,877 grams of ammonium phosphor molybdate containing 31 grams of phosphorus.

Q: How does the magnesium method estimate phosphorus?

The organic compound is reacted with fuming nitric acid, and magnesia is added to form magnesium ammonium phosphate precipitate. That precipitate is ignited to obtain magnesium pyrophosphate.

Q: Which products are used to calculate phosphorus in the two methods?

The ammonium molybdate method uses ammonium phosphor molybdate, while the magnesium method ultimately uses magnesium pyrophosphate. The stated calculation relationships are 31 × M1 ÷ 1,877 for the first product and 62 × M1 ÷ 222 for the second.

Summary & Key Takeaways

• There are two methods for estimating the percentage of phosphorus in organic compounds: one using ammonium molybdate and the other using magnesium.

• The ammonium molybdate method involves treating the organic compound with fuming nitric acid, followed by ammonia and ammonium molybdate, resulting in the formation of ammonium phosphor molybdate precipitate.

• The magnesium method involves reacting the organic compound with fuming nitric acid and adding magnesia, leading to the formation of magnesium ammonium phosphate precipitate, which is eventually ignited to obtain magnesium pyrophosphate.