Introduction
Phosphine, or PH3, is a fascinating yet hazardous chemical compound. This colorless gas, known for its pungent garlic-like odor, plays a significant role in industries like agriculture and electronics. However, its toxicity and flammability require precise handling. A common question in chemistry is, “What is the mass of 3.81 mol of PH3?” This calculation is vital for professionals and students working with chemical quantities. In this article, we explore phosphine’s properties, uses, and how to calculate the mass of 3.81 moles of PH3. By the end, you’ll master this essential chemistry concept.
What is Phosphine (PH3)?
Phosphine (PH3) is the simplest phosphine, featuring one phosphorus atom bonded to three hydrogen atoms. Discovered in 1783 by Philippe Gengembre, a student of Antoine Lavoisier, it was initially mistaken for a gaseous form of phosphorus. Lavoisier later clarified it as a phosphorus-hydrogen compound (Phosphine History). Its trigonal pyramidal structure results from a lone pair of electrons on phosphorus, affecting its chemical behavior.
Physical and Chemical Properties
Phosphine is a colorless gas with a disagreeable odor resembling rotten fish or garlic. It is highly toxic, posing severe risks to the respiratory system at low concentrations. Additionally, it is flammable and can ignite spontaneously in air, especially when contaminated with diphosphine (P2H4). PH3 is sparingly soluble in water but dissolves well in organic solvents. As a Lewis base, it donates its lone pair of electrons in reactions (Phosphine Properties).
| Property | Description |
| Chemical Formula | PH3 |
| Molar Mass | 34.00 g/mol |
| Odor | Rotten fish or garlic-like |
| Toxicity | Highly toxic, harmful at 50 ppm |
| Flammability | Spontaneously flammable in impure form |
| Solubility | Sparingly soluble in water |
Industrial and Scientific Uses
Phosphine serves multiple purposes across industries. Firstly, it acts as a fumigant in agriculture, controlling pests in stored grains. Secondly, the semiconductor industry uses it as a dopant to enhance electrical properties. Thirdly, it appears in chemical synthesis as a reducing agent. Interestingly, phosphine’s spontaneous combustion property is utilized in Holme’s signal for maritime applications. Recently, its detection in Venus’s atmosphere sparked discussions about potential life indicators (Phosphine in Venus).
Understanding Moles and Molar Mass
To answer, “What is the mass of 3.81 mol of PH3?” we must grasp the concepts of moles and molar mass. These are foundational in chemistry for quantifying substances.
What is a Mole?
A mole is a unit representing 6.022 × 10^23 particles, known as Avogadro’s constant. Whether atoms, molecules, or ions, one mole contains this exact number of entities. For instance, one mole of PH3 includes 6.022 × 10^23 PH3 molecules. This unit bridges microscopic particles to measurable macroscopic quantities, simplifying chemical calculations.
What is Molar Mass?
Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol). It is calculated by summing the atomic masses of all atoms in a molecule. For PH3, we compute:
- Phosphorus (P): 30.97 g/mol
- Hydrogen (H): 1.008 g/mol × 3 = 3.024 g/mol
- Total: 30.97 + 3.024 = 34.00 g/mol
Thus, one mole of PH3 weighs 34.00 grams. This value is critical for converting between moles and mass (Molar Mass Basics).
Importance of Molar Mass
Molar mass enables chemists to determine the mass of a substance from its moles or vice versa. This is essential for stoichiometry, where precise quantities ensure balanced chemical reactions. For PH3, knowing its molar mass helps in preparing exact amounts for industrial processes or laboratory experiments, ensuring safety and efficiency.
Calculating the Mass of 3.81 Mol of PH3
Now, let’s calculate the mass of 3.81 moles of PH3. The formula is:
[ \text{Mass} = \text{Number of moles} \times \text{Molar mass} ]
Step-by-Step Calculation
- Identify the molar mass: As calculated, PH3’s molar mass is 34.00 g/mol.
- Determine the moles: The problem specifies 3.81 moles.
- Apply the formula:
[ \text{Mass} = 3.81 , \text{mol} \times 34.00 , \text{g/mol} ]
- Perform the multiplication:
[ 3.81 \times 34.00 = 129.54 , \text{g} ]
Therefore, the mass of 3.81 moles of PH3 is 129.54 grams. This precise calculation is vital for applications requiring exact quantities of phosphine.
Related Calculations and Concepts
To deepen our understanding, let’s explore related calculations and concepts involving PH3 and molar mass.
Molar Mass of Other Phosphines
Phosphine is the simplest phosphine, but compounds like diphosphine (P2H4) exist. Calculating their molar masses follows the same principle. For P2H4:
- Phosphorus: 2 × 30.97 = 61.94 g/mol
- Hydrogen: 4 × 1.008 = 4.032 g/mol
- Total: 61.94 + 4.032 = 65.972 g/mol
This comparison highlights how molecular complexity affects molar mass (Phosphine Variants).
Stoichiometry with PH3
Molar mass is crucial in stoichiometry. Consider the oxidation of PH3 to phosphoric acid (H3PO4):
[ 2PH3 + 4O2 \rightarrow H3PO4 + H2O ]
Knowing the mass of 3.81 moles of PH3 (129.54 g) allows us to calculate the oxygen required or the H3PO4 produced, ensuring accurate reaction planning.
Density and Volume of PH3
As a gas, PH3’s density can be calculated using its molar mass and the ideal gas law. At standard temperature and pressure (STP), where one mole of gas occupies 22.4 liters:
[ \text{Density} = \frac{\text{Molar mass}}{\text{Molar volume}} = \frac{34.00 , \text{g/mol}}{22.4 , \text{L/mol}} \approx 1.518 , \text{g/L} ]
This density is useful for handling PH3 in gaseous form, such as in fumigation processes (PH3 Density).
FAQs
What is the molar mass of PH3?
The molar mass of PH3 is approximately 34.00 g/mol, calculated from one phosphorus (30.97 g/mol) and three hydrogens (1.008 g/mol each).
How do you calculate moles from mass?
Use the formula: [ \text{Number of moles} = \frac{\text{Mass}}{\text{Molar mass}} ]. For example, 129.54 g of PH3 divided by 34.00 g/mol yields 3.81 moles.
Is PH3 dangerous?
Yes, PH3 is highly toxic and flammable. Inhalation can harm the respiratory system, and it may ignite spontaneously in air (PH3 Safety).
What are common uses of PH3?
Phosphine is used as a fumigant, a dopant in semiconductors, and in chemical synthesis. It also appears in Holme’s signal due to its flammability.
Can PH3 be liquefied?
Yes, PH3 can be liquefied under pressure or at low temperatures, with a boiling point of -87.7 °C (PH3 Physical Properties).
Conclusion
Calculating the mass of 3.81 moles of PH3 reveals its weight as 129.54 grams, a straightforward yet critical task in chemistry. Phosphine, with its toxic and flammable nature, demands careful handling in its diverse applications, from pest control to semiconductor manufacturing. Understanding moles and molar mass empowers you to perform precise chemical calculations. Continue exploring chemistry to unlock more insights into fascinating compounds like PH3. For further learning, dive into stoichiometry or gas laws to enhance your skills!
