Question

when gaseous phosphorus pentachloride, pcl₅, is heated to moderate temperatures, it decomposes in to the gaseous phosphorus trichloride and chlorine gas. given that 87.9 kj of heat is consumed in the process at a constant pressure of 1.18 atm, what is the balanced thermochemical equation for this reaction? fill in the values for the coefficients (if the coefficient is 1, enter the number 1, do not leave blank), phase labels, and enthalpy. pcl₅()→pcl₃()+cl₂();δh=kj question 4 1 pts gaseous ammonia reacts with oxygen to produce nitrogen and water vapor according to the following thermochemical equation: 4nh₃(g)+3o₂(g)→2n₂(g)+6h₂o(g);δh = - 1232 kj how much heat is released or absorbed (given by the sign of your answer) when 35.96 g of ammonia are reacted in excess oxygen? report your answer in kilojoules to 4 sig figs, but do not include the units in the answer.

Explanation:

Step1: Calculate the molar mass of \(NH_3\)

The molar mass of \(N = 14.01\space g/mol\) and \(H= 1.008\space g/mol\). For \(NH_3\), \(M=(14.01 + 3\times1.008)\space g/mol= 17.034\space g/mol\)

Step2: Calculate the number of moles of \(NH_3\)

Using the formula \(n=\frac{m}{M}\), where \(m = 35.96\space g\) and \(M = 17.034\space g/mol\). So \(n=\frac{35.96}{17.034}\space mol\approx2.111\space mol\)

Step3: Relate moles of \(NH_3\) to \(\Delta H\)

From the thermochemical equation \(4NH_3(g)+3O_2(g)\to2N_2(g)+6H_2O(g);\Delta H=- 1232\space kJ\), for \(4\space mol\) of \(NH_3\), the enthalpy change is \(-1232\space kJ\). Let \(x\) be the enthalpy change for \(2.111\space mol\) of \(NH_3\). Using the proportion \(\frac{x}{2.111}=\frac{- 1232}{4}\)

$$x=\frac{-1232\times2.111}{4}$$

$$x=-650.0$$

Answer:

\(-650.0\)