What is the mass of 3.81 mol of PH3?
Understand the Problem
The question is asking for the calculation of the mass of phosphine (PH3) given its amount in moles (3.81 mol). To find the mass, we will use the formula: mass = moles × molar mass. We need to calculate the molar mass of PH3 and then multiply it by 3.81 mol.
Answer
The mass of phosphine (PH₃) is approximately 129.6 g.
Answer for screen readers
The mass of phosphine (PH₃) is approximately 129.6 g.
Steps to Solve

Calculate the molar mass of phosphine (PH₃)
To find the molar mass, we will add the atomic masses of all the atoms in the phosphine molecule:
 Phosphorus (P) has an atomic mass of about 31.00 g/mol
 Hydrogen (H) has an atomic mass of about 1.01 g/mol
Since there are one phosphorous atom and three hydrogen atoms in PH₃, we calculate as follows:
$$ \text{Molar mass of PH}_3 = 31.00 , \text{g/mol} + (3 \times 1.01 , \text{g/mol}) $$

Perform the multiplication
After calculating the molar mass, we multiply it by the number of moles to find the mass:
Let’s calculate the molar mass from step 1:
$$ \text{Molar mass of PH}_3 = 31.00 , \text{g/mol} + 3.03 , \text{g/mol} = 34.03 , \text{g/mol} $$
Now, we calculate the mass:
$$ \text{Mass} = \text{Moles} \times \text{Molar mass} = 3.81 , \text{mol} \times 34.03 , \text{g/mol} $$

Finish the calculations
Now, we can compute the final mass:
$$ \text{Mass} = 3.81 , \text{mol} \times 34.03 , \text{g/mol} \approx 129.6 , \text{g} $$
The mass of phosphine (PH₃) is approximately 129.6 g.
More Information
This calculation shows how to find the mass of a compound from its moles by using its molar mass. In chemistry, understanding how to convert between moles and mass is essential for stoichiometry and reactions involving substances.
Tips
 Forgetting to multiply the atomic mass of hydrogen by the number of hydrogen atoms present in the compound.
 Miscalculating the multiplication when finding the mass from moles and molar mass. It's crucial to ensure that the order of operations is followed correctly.