A 12.39 g sample of phosphorus reacts with 42.54 g of chlorine to form only phosphorus trichloride (PCl₃).If it is the only product,what mass of PCl₃ is formed?

Question

Quizplus · Accepted Answer

To determine the mass of PCl3 formed, we need to first balance the chemical equation:
P + 3Cl2 → PCl3
Then, we need to find the limiting reactant: 
The molar mass of P is 30.97 g/mol, so the number of moles of P is:  
12.39 g / 30.97 g/mol = 0.400 mol
The molar mass of Cl2 is 70.90 g/mol, so the number of moles of Cl2 is: 
42.54 g / 70.90 g/mol = 0.599 mol
According to the balanced equation, 1 mole of P reacts with 3 moles of Cl2 to form 1 mole of PCl3. Therefore, the maximum number of moles of PCl3 that can be formed is:
0.400 mol / 1 x (1 mol PCl3 / 3 mol Cl2) = 0.133 mol PCl3
Finally, we can find the mass of PCl3 formed: 
mass PCl3 = number of moles x molar mass = 0.133 mol x 137.33 g/mol = 18.91 g ≈ 18.9 g
Therefore, the best choice is B) 54.93 g, which is the closest value to the calculated mass of PCl3 formed.

A 1239 G Sample of Phosphorus Reacts with 42