When calculating the mass of a chemical compound given in moles, understanding the molar mass of the substance is essential. In this article, we will thoroughly analyze phosphine (PH₃), break down its molecular weight, and accurately determine the mass of 3.81 moles of PH₃. Additionally, we’ll explore essential chemical properties of phosphine, its applications, and relevant safety measures to ensure a comprehensive understanding.
Understanding the Molecular Composition of PH₃
Phosphine, with the chemical formula PH₃, is composed of one phosphorus (P) atom and three hydrogen (H) atoms. It is a colorless, flammable, and toxic gas with a garlicky odor, often used in semiconductor industries and pest control.
To determine its molar mass, we sum the atomic masses of all atoms in one molecule:
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Atomic mass of Phosphorus (P) = 30.97 g/mol
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Atomic mass of Hydrogen (H) = 1.008 g/mol
Thus, the molar mass of PH₃ = 30.97 + (3 × 1.008)
= 30.97 + 3.024
= 33.994 g/mol
We round this to 34.00 g/mol for practical use.
Calculating the Mass of 3.81 mol of PH₃
Now that we know the molar mass of PH₃ is 34.00 g/mol, we can easily calculate the mass of 3.81 moles using the formula:
Mass = Moles × Molar Mass
Mass = 3.81 mol × 34.00 g/mol
Mass = 129.54 grams
✅ Final Answer: The mass of 3.81 mol of PH₃ is 129.54 grams.
Why Is Molar Mass Important in Chemistry?
Understanding molar mass enables chemists to:
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Predict reactant and product quantities in reactions
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Perform stoichiometric calculations
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Determine chemical yields
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Design industrial processes with precision
Properties and Characteristics of Phosphine (PH₃)
Physical Properties:
| Property | Value |
|---|---|
| Molecular Formula | PH₃ |
| Molar Mass | 34.00 g/mol |
| Appearance | Colorless gas |
| Odor | Garlic-like, fishy |
| Density | 1.529 g/L at 0 °C and 1 atm |
| Melting Point | -132.8 °C |
| Boiling Point | -87.7 °C |
| Solubility in Water | Slightly soluble |
Chemical Properties:
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Highly reactive with oxidizing agents
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Burns with a luminous flame, producing phosphorus pentoxide
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Acts as a reducing agent in chemical reactions
Industrial and Scientific Uses of PH₃
Despite its toxicity, PH₃ plays a pivotal role in several fields:
1. Semiconductor Industry
Phosphine is used for doping silicon wafers with phosphorus to alter electrical properties during microchip manufacturing.
2. Agricultural Fumigation
PH₃ is used as a fumigant for stored grain and other agricultural products, effectively eliminating pests such as weevils, moths, and beetles.
3. Organophosphorus Chemistry
It serves as a starting material for organophosphorus compounds, including ligands for catalysts in organometallic chemistry.
4. Chemical Synthesis
PH₃ is a key reagent in various laboratory syntheses, particularly for creating phosphine derivatives.
Safety and Hazards of Phosphine Gas
Handling PH₃ requires caution due to its toxicity and flammability:
⚠️ Toxicity:
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PH₃ is extremely poisonous by inhalation.
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Exposure can lead to respiratory irritation, nausea, vomiting, and even death in high concentrations.
⚠️ Flammability:
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PH₃ ignites spontaneously in air at room temperature when contaminated with diphosphine (P₂H₄).
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It forms explosive mixtures with air.
🧯 Handling Measures:
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Store in cylinders under pressure.
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Use gas detection systems in laboratories or industries.
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Employ proper ventilation and personal protective equipment (PPE).
Phosphine in Environmental and Biological Contexts
🌱 Environmental Impact:
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PH₃ does not persist in the environment.
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It is oxidized rapidly in the atmosphere.
🧬 Biological Relevance:
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Though not naturally produced by humans, small traces of PH₃ have been detected in anaerobic environments, including marshes and landfills.
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It gained attention due to its potential detection on Venus, sparking interest in astrobiology.
Converting Between Moles and Mass of PH₃ – A Quick Reference Table
| Moles (mol) | Mass of PH₃ (g) |
|---|---|
| 1 | 34.00 |
| 2 | 68.00 |
| 3.81 | 129.54 |
| 5 | 170.00 |
| 10 | 340.00 |
This table provides a quick reference to determine mass for various mole values of PH₃ using its molar mass.
Conclusion: Accurate Chemical Calculations Matter
Accurately calculating the mass of 3.81 mol of PH₃ as 129.54 grams demonstrates a foundational skill in chemistry. From laboratory research to industrial application, precise measurements are critical in ensuring efficiency, safety, and desired chemical outcomes. Understanding molar mass and stoichiometry not only allows for correct formulations but also optimizes processes across scientific disciplines.
