Question

how much heat is evolved when 320 g of so₂ is burned according to the chemical equation shown below? 2 so₂(g) + o₂(g) → 2 so₃(g) δh° = -198 kj 546 kj 185 kj 371 kj 885 kj 495 kj

Explanation:

Step1: Calculate the molar mass of \(SO_2\)

The molar mass of \(S = 32\space g/mol\) and \(O = 16\space g/mol\). For \(SO_2\), \(M=(32 + 2\times16)\space g/mol=64\space g/mol\)

Step2: Calculate the number of moles of \(SO_2\)

Using the formula \(n=\frac{m}{M}\), where \(m = 320\space g\) and \(M = 64\space g/mol\). So \(n=\frac{320\space g}{64\space g/mol}=5\space mol\)

Step3: Relate moles of \(SO_2\) to \(\Delta H\)

From the equation \(2SO_2(g)+O_2(g)\to2SO_3(g)\space \Delta H^0=- 198\space kJ\), for \(2\space mol\) of \(SO_2\), heat evolved is \(198\space kJ\).
For \(1\space mol\) of \(SO_2\), heat evolved \(q=\frac{198\space kJ}{2}=99\space kJ\)
For \(n = 5\space mol\) of \(SO_2\), heat evolved \(Q=99\space kJ/mol\times5\space mol = 495\space kJ\)

Answer:

\(495\space kJ\) (the fifth option)