A chemical reaction, A(s) $\rarr$ B(s)+ C(g), occurs when substance A is strongly heated. The molecular mass of the gaseous product was to be determined from the following experimental data: Mass of A before reaction starts: 4.962 g
Mass of A after reaction finishes: 0 g Mass of residue (B)after cooling and weighing when no more gas was evolved: 3.684 g When all of the gas C evolved was collected and stored in a 658.5 mL glass vessel at 30.4 °C, the gas exerted a pressure of 748.5 torr.From this data, determine the apparent molecular mass of C, assuming it behaves as an ideal gas.

Question

Quizplus · Accepted Answer

The mass of gas C is the initial mass of A minus the mass of residue B, which is 4.962 g - 3.684 g = 1.278 g. Using the ideal gas law, PV = nRT, we can find the number of moles of C. Convert pressure to atm (748.5 torr = 0.984 atm), volume to liters (658.5 mL = 0.6585 L), and temperature to Kelvin (30.4 °C = 303.55 K). Using R = 0.0821 L atm/mol K, n = (0.984 atm * 0.6585 L) / (0.0821 L atm/mol K * 303.55 K) = 0.0260 mol. The molecular mass is mass/moles = 1.278 g / 0.0260 mol = 49.1 g/mol.

A Chemical Reaction, A(s) →\rarr→ B(s)+ C(g), Occurs When Substance a Is Strongly Heated

A Chemical Reaction, A(s) $\rarr$ B(s)+ C(g), Occurs When Substance a Is Strongly Heated