20 mL of liquid pyridine ( C₅H₅N , specific gravity 0.79 ) is completely burnt in excess oxygen. Find the total volume of the gaseous products measured at STP. (Assume water formed is in the liquid state and molar volume of a gas at STP is 22.4 L )

Step-by-step solution

Mass of pyridine ( C₅H₅N ) = Volume Density = 20 0.79 = 15.8 g Molar mass of C₅H₅N = (5 12) + (5 1) + 14 = 79 g/mol Moles of pyridine = 15.8 79 = 0.2 mol The balanced chemical equation for the combustion of pyridine is: C₅H₅N(l) + 25 4 O₂(g) 5 CO₂(g) + 5 2 H₂O(l) + 1 2 N₂(g) Since water is in the liquid state, the gaseous products are CO₂ and N₂ . Moles of gaseous products per mole of pyridine = 5 + 1 2 = 5.5 mol Total moles of gaseous products formed = 0.2 5.5 = 1.1 mol Volume of gaseous products at STP = 1.1 22.4