Question

question 9
determine the amount of no₂ produced, in g. if -622 kj of heat is given off, according to the following equation:
2 no(g) + o₂(g) → 2 no₂(g)
δh = -114.6 kj/mol
report your answer to the nearest whole number.

Explanation:

Step1: Calculate moles of reaction

Given \(\Delta H=- 114.6\space kJ/mol\) (per mole of reaction). The heat given off \(q = 622\space kJ\).
The number of moles of reaction \(n=\frac{q}{\vert\Delta H\vert}=\frac{622\space kJ}{114.6\space kJ/mol}\approx5.427\space mol\)

Step2: Relate moles of reaction to moles of \(NO_2\)

From the balanced equation \(2NO(g)+O_2(g)\to2NO_2(g)\), for each mole of reaction, \(2\space mol\) of \(NO_2\) is produced.
So moles of \(NO_2,n_{NO_2}=2\times n = 2\times5.427\space mol = 10.854\space mol\)

Step3: Calculate mass of \(NO_2\)

The molar mass of \(NO_2,M=(14 + 2\times16)\space g/mol=46\space g/mol\)
Mass of \(NO_2,m = n_{NO_2}\times M=10.854\space mol\times46\space g/mol = 500.284\space g\approx500\space g\)

Answer:

\(500\)