Hydrates Original Scenario-Based Download PDF

Questions

1. 1.

   Inside a submerged oceanic research dome on an icy moon, an environmental moisture regulator utilizes crystalline calcium chloride dihydrate, $\text{CaCl}_2 \cdot 2\text{H}_2\text{O}$, to balance internal vapor levels. A maintenance android retrieves a sample containing exactly 14.7 g of these pure crystals for diagnostic mass spectrometry. How many water molecules are chemically trapped within this 14.7 g sample? (Molar masses: $\text{Ca} = 40.0\text{ g/mol}$, $\text{Cl} = 35.5\text{ g/mol}$, $\text{H} = 1.0\text{ g/mol}$, $\text{O} = 16.0\text{ g/mol}$; Avogadro's number = $6.02 \times 10^{23}\text{ molecules/mol}$)

   • A) $3.01 \times 10^{22}$
   • B) $6.02 \times 10^{22}$
   • C) $1.20 \times 10^{23}$
   • D) $3.61 \times 10^{23}$
2. 2.

   In a floating atmospheric laboratory within the clouds of Venus, scientists calibrate a chemical humidity beacon that changes color upon dehydration, relying on crystalline cobalt(II) chloride hexahydrate, $\text{CoCl}_2 \cdot 6\text{H}_2\text{O}$. To establish the baseline threshold of the sensor, the automated analyzer must compute the theoretical mass percentage of water of crystallization in this compound. What is the percent by mass of water in $\text{CoCl}_2 \cdot 6\text{H}_2\text{O}$? (Molar masses: $\text{Co} = 59.0\text{ g/mol}$, $\text{Cl} = 35.5\text{ g/mol}$, $\text{H} = 1.0\text{ g/mol}$, $\text{O} = 16.0\text{ g/mol}$)

   • A) 7.56%
   • B) 83.1%
   • C) 54.6%
   • D) 45.4%
3. 3.

   In an orbital synthesis facility aboard a deep-space probe, researchers analyze an extraterrestrial mineral crystal identified as a dihydrate with the formula $\text{MCl}_2 \cdot 2\text{H}_2\text{O}$. When a 7.35 g sample of this crystal is heated until complete dehydration occurs, 5.55 g of anhydrous $\text{MCl}_2$ remains. Based on these data, what is the atomic mass of the unknown metal M? (Molar masses: $\text{H}_2\text{O} = 18.0\text{ g/mol}$, $\text{Cl} = 35.5\text{ g/mol}$)

   • A) 40.0 g/mol
   • B) 55.8 g/mol
   • C) 75.5 g/mol
   • D) 111.0 g/mol
4. 4.

   To generate emergency drinking water in a Martian research habitat, the crew bakes a reserve of crystalline sodium carbonate decahydrate, $\text{Na}_2\text{CO}_3 \cdot 10\text{H}_2\text{O}$. If the habitat's life-support recycler requires 90.0 g of pure liquid water, what mass of the hydrate crystals must undergo complete thermal dehydration? (Molar masses: $\text{Na}_2\text{CO}_3 = 106.0\text{ g/mol}$, $\text{H}_2\text{O} = 18.0\text{ g/mol}$)

   • A) 143 g
   • B) 286 g
   • C) 53.0 g
   • D) 1430 g
5. 5.

   An expedition team exploring an alien geothermal cavern recovers a shimmering crystalline hydrate with the formula $\text{MX}_2 \cdot n\text{H}_2\text{O}$. When a 4.88 g sample is heated to constant mass in a desiccating chamber, 3.08 g of anhydrous $\text{MX}_2$ remains. Given that the molar mass of $\text{MX}_2$ is 154 g/mol and the molar mass of $\text{H}_2\text{O}$ is 18.0 g/mol, what is the value of the integer $n$?

   • A) 2
   • B) 3
   • C) 5
   • D) 7