Question

The mass of P4 (molar mass = 123.88 g/mol) that completely reacts with 7.80 g of H2 (molar mass = 2.02 g/mol). P4 + 6H2 -> 4PH3

Answer 1

To find the mass of P4 that reacts with 7.80 g of H2, calculate the moles of H2, use the stoichiometry to find the moles of P4 needed, and then convert that to mass; the answer is 79.71 g of P4.

Step-by-step explanation:

To find the mass of P4 that completely reacts with 7.80 g of H2, we start by determining the number of moles of H2 using its molar mass. Then, we apply the stoichiometry of the given chemical equation P4 + 6H2 -> 4PH3 to find the moles of P4 needed. Finally, we convert the moles of P4 into mass using the molar mass of P4.

First, calculate the moles of H2:

1. 
   
2. Number of moles = mass (g) / molar mass (g/mol)
3. 
   
4. Number of moles of H2 = 7.80 g / 2.02 g/mol
5. 
   
6. Number of moles of H2 = 3.86 moles

Next, use the stoichiometry of the reaction to find the moles of P4:

1. 
   
2. According to the balanced equation, 6 moles of H2 react with 1 mole of P4.
3. 
   
4. Moles of P4 = Moles of H2 / 6
5. 
   
6. Moles of P4 = 3.86 moles / 6
7. 
   
8. Moles of P4 = 0.643 moles

Now, calculate the mass of P4:

1. 
   
2. Mass of P4 = Moles of P4 * Molar mass of P4
3. 
   
4. Mass of P4 = 0.643 moles * 123.88 g/mol
5. 
   
6. Mass of P4 = 79.71 g

Therefore, 79.71 g of P4 will completely react with 7.80 g of H2.