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 885 kj 185 kj 495 kj 371 kj 546 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 \(2SO_2(g)+O_2(g)\to2SO_3(g)\space\Delta H^{\circ}=- 198\space kJ\), 2 moles of \(SO_2\) give \(\Delta H=-198\space kJ\).
Let \(x\) be the heat evolved for 5 moles of \(SO_2\). Using proportion \(\frac{x}{5}=\frac{- 198}{2}\)

$$x=\frac{-198\times5}{2}=-495\space kJ$$

The negative sign indicates heat is evolved.

Answer:

495 kJ