Answer to Question #168040 in Chemistry for Ava Brooke

Question

How much phosphorus in grams is required to release 282.79 kJ of heat?

5 Ni + 2 P -> Ni₅P₂  

△ H= 436 kJ/mol

Answer 1

Solution:

The balanced thermochemical equation:

5Ni + 2P → Ni₅P₂, △H = 436 kJ/mol

 

The equivalences for this thermochemical equation are:

5 mol Ni ⇔ 2 mol P ⇔ 1 mol Ni₅P₂ ⇔ 436 kJ/mol

 

Using the thermochemical equation to determine the moles of phosphorus (P):

282.79 kJ × (2 mol P / 436 kJ) = 1.2972 mol

Mass of P = Moles of P × Molar mass of P

Molar mass of P is 30.9738 g mol^-1.

Hence,

Mass of P = 1.2972 mol × 30.9738 g mol^-1 = 40.179 g = 40.18 g

Mass of P = 40.18 g

Answer: 40.18 grams of phosphorus (P) is required to release 282.79 kJ of heat.