Percent composition Original Scenario-Based Download PDF

Questions

1. 1.

   To harvest vital water reserves on an arid exoplanet, planetary engineers thermally extract moisture from mineral veins of calcium sulfate dihydrate ($CaSO_4 \cdot 2H_2O$). To program the dehydration kilns for optimal extraction yield, the team must find the exact mass percentage of water bound inside the crystal structure. Given the molar masses of calcium (40.0 g/mol), sulfur (32.0 g/mol), oxygen (16.0 g/mol), and hydrogen (1.0 g/mol), what is the percent composition by mass of water in $CaSO_4 \cdot 2H_2O$?

   • A) 11.7%
   • B) 20.9%
   • C) 26.5%
   • D) 36.0%
2. 2.

   A team of xenogeologists exploring the subterranean caverns of a hollow moon discovers an ancient metallic artifact composed entirely of nickel and sulfur. To analyze its protective shielding, an automated laser pyrolyzer breaks down a 50.0 g sample of the artifact, isolating 32.5 g of pure nickel and releasing the remaining mass as sulfur gas. Based on these laboratory findings, what is the percent composition by mass of sulfur in the artifact?

   • A) 65.0%
   • B) 53.8%
   • C) 35.0%
   • D) 17.5%
3. 3.

   In a floating bioluminescent sky-sanctuary on the gas giant Zephyria, botanists synthesize specialized fertilizer crystals of calcium phosphate ($Ca_3(PO_4)_2$) to nourish high-altitude hydroponic aerogardens. To calibrate the autonomous dispersal drones for optimal nutrient delivery, the flight chemists must calculate the exact mass percentage of phosphorus present in the compound. Given molar masses of 40.0 g/mol for calcium, 31.0 g/mol for phosphorus, and 16.0 g/mol for oxygen, what is the percent composition by mass of phosphorus in $Ca_3(PO_4)_2$?

   • A) 20.0%
   • B) 10.0%
   • C) 38.7%
   • D) 41.3%
4. 4.

   In the subterranean crystalline caverns of the volcanic planet Vulcanus, geochemists harvest deep-red mineral veins of iron(III) oxide ($Fe_2O_3$) to manufacture protective radiation shielding for exploration rovers. To program the autonomous smelting furnace for maximum extraction efficiency, the mission specialists must calculate the exact mass percentage of iron present in the mineral. Given atomic masses of 56.0 g/mol for iron and 16.0 g/mol for oxygen, what is the percent composition by mass of iron in $Fe_2O_3$?

   • A) 35.0%
   • B) 70.0%
   • C) 53.8%
   • D) 30.0%
5. 5.

   A team of astrochemists aboard the deep-space vessel Chronos recovers an icy comet core containing frozen deposits of ammonium nitrate ($NH_4NO_3$) to synthesize propellant oxidizers. To calibrate the ship's automated molecular breakdown unit, the technicians must determine the exact proportion of oxidizer mass contributed by oxygen. Given the molar masses of nitrogen (14.0 g/mol), hydrogen (1.0 g/mol), and oxygen (16.0 g/mol), what is the percent composition by mass of oxygen in $NH_4NO_3$?

   • A) 60.0%
   • B) 35.0%
   • C) 37.5%
   • D) 20.0%