Molecular formulas Original Scenario-Based Practice

Questions

1. 1.

   An exploration crew investigating an abandoned orbital research platform recovers an unlabelled canister of liquid thruster propellant. When a 0.0500 mol sample of the vaporized compound is completely decomposed by an electric discharge, it yields 1.12 L of $\text{N}_2$ gas and 2.24 L of $\text{H}_2$ gas measured at standard temperature and pressure (STP). Based on these decomposition data, what is the molecular formula of the propellant?

   • A) $\text{NH}_2$
   • B) $\text{NH}_3$
   • C) $\text{N}_2\text{H}_2$
   • D) $\text{N}_2\text{H}_4$
2. 2.

   A deep-space drone surveying an ancient orbital shipyard discovers a sealed pressurization cylinder filled with an amber oxidant used in stasis thrusters. Quantitative analysis shows that the volatile substance consists of 30.45% nitrogen and 69.55% oxygen by mass. An onboard mass spectrometer subsequently establishes that the compound has a molar mass of 92.02 g/mol. Given atomic molar masses of 14.01 g/mol for N and 16.00 g/mol for O, what is the molecular formula of this oxidant?

   • A) $\text{NO}_2$
   • B) $\text{N}_2\text{O}_3$
   • C) $\text{N}_2\text{O}_4$
   • D) $\text{N}_3\text{O}_6$
3. 3.

   An environmental probe patrolling a subterranean terraforming dome samples a volatile fragrance released by bioluminescent mosses. Laboratory analysis of a 0.200 mol sample of this pure compound determines that it contains 14.4 g of carbon, 2.40 g of hydrogen, and 6.40 g of oxygen. Assuming atomic molar masses of 12.0 g/mol for C, 1.0 g/mol for H, and 16.0 g/mol for O, what is the molecular formula of this fragrant substance?

   • A) $\text{C}_3\text{H}_6\text{O}$
   • B) $\text{C}_3\text{H}_6\text{O}_2$
   • C) $\text{C}_6\text{H}_6\text{O}_2$
   • D) $\text{C}_6\text{H}_{12}\text{O}_2$
4. 4.

   Deep beneath the ice sheet of an alien moon, an exploration rover isolates a glowing organic crystal from a hydrothermal vent. Quantitative analysis reveals that the substance has an empirical formula of $\text{C}_3\text{H}_4\text{O}_3$ and an experimentally determined molar mass of 176 g/mol. What is the molecular formula of this mysterious compound?

   • A) $\text{C}_6\text{H}_8\text{O}_6$
   • B) $\text{C}_3\text{H}_4\text{O}_3$
   • C) $\text{C}_9\text{H}_{12}\text{O}_9$
   • D) $\text{C}_6\text{H}_{12}\text{O}_6$

Answers and step-by-step solutions appear after you finish the test.