Understanding the relationship between moles and mass is fundamental in chemistry. One common question is: “What is the mass of 3.81 mol of PH₃ (phosphine)?” To answer this, we need to explore the concept of molar mass and how it applies to chemical compounds like PH₃.
In this article, we’ll break down the steps to calculate the mass of a given number of moles, explain the properties of phosphine, and provide additional insights into its applications and safety considerations.
Table of Contents
Understanding Moles and Molar Mass
What is a Mole?
A mole (mol) is a unit in chemistry that represents 6.022 × 10²³ particles (Avogadro’s number). It allows chemists to count atoms, molecules, or ions in measurable quantities.
What is Molar Mass?
Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). It is calculated by summing the atomic masses of all atoms in a molecule.
Calculating the Mass of 3.81 mol of PH₃
Step 1: Determine the Molar Mass of PH₃
Phosphine (PH₃) consists of:
- 1 phosphorus (P) atom
- 3 hydrogen (H) atoms
Using the periodic table:
- Atomic mass of P = 30.97 g/mol
- Atomic mass of H = 1.01 g/mol
Now, calculate the molar mass of PH₃:Molar Mass of PH₃=(1×30.97)+(3×1.01)=30.97+3.03=34.00 g/molMolar Mass of PH₃=(1×30.97)+(3×1.01)=30.97+3.03=34.00 g/mol
Step 2: Calculate the Mass of 3.81 mol of PH₃
Now that we know the molar mass, we can find the mass using:Mass=Number of Moles×Molar MassMass=Number of Moles×Molar MassMass=3.81 mol×34.00 g/mol=129.54 gMass=3.81 mol×34.00 g/mol=129.54 g
Final Answer:
The mass of 3.81 moles of PH₃ is 129.54 grams.
Properties and Uses of Phosphine (PH₃)
Chemical Properties
- Formula: PH₃
- Appearance: Colorless gas
- Odor: Rotten fish or garlic-like smell (highly toxic)
- Density: Heavier than air
- Flammability: Highly flammable
Industrial Applications
- Pesticides & Fumigants: Used to control pests in stored grains.
- Semiconductor Industry: Helps in doping silicon-based electronics.
- Chemical Synthesis: Acts as a reducing agent in organic reactions.
Safety Considerations
- Toxicity: Extremely poisonous—exposure can be fatal.
- Handling: Requires proper ventilation and protective equipment.
FAQs About Moles and Phosphine
1. How do you find the molar mass of a compound?
To find the molar mass:
- Identify each element in the compound.
- Multiply each element’s atomic mass by its number of atoms.
- Sum all the values to get the total molar mass.
2. Why is phosphine dangerous?
Phosphine is toxic when inhaled and can cause respiratory failure. It is also flammable, posing explosion risks.
3. Can moles be converted to grams for any substance?
Yes, as long as you know the substance’s molar mass, you can convert moles to grams using:Mass (g)=Moles (mol)×Molar Mass (g/mol)Mass (g)=Moles (mol)×Molar Mass (g/mol)
4. What is the difference between molecular mass and molar mass?
- Molecular mass is the mass of a single molecule in atomic mass units (amu).
- Molar mass is the mass of one mole of a substance in grams per mole (g/mol).
5. How is phosphine produced industrially?
Phosphine is commonly produced by reacting white phosphorus (P₄) with a strong base or by hydrolyzing metal phosphides.
Conclusion
Calculating the mass of a given number of moles is a straightforward process once the molar mass is known. For 3.81 moles of PH₃, the mass is 129.54 grams. Understanding these calculations is essential for chemical measurements, laboratory work, and industrial applications.
Phosphine, while useful in various industries, must be handled with extreme caution due to its toxicity and flammability. Always follow safety protocols when working with hazardous chemicals.
By mastering mole-to-mass conversions, students and professionals can better navigate chemical equations and real-world applications.
