Chemical equations Original Scenario-Based Practice

Questions

1. 1.

   In an off-world orbital foundry, metallic iron is recovered from extraterrestrial regolith using carbon monoxide according to the unbalanced chemical equation: $\text{Fe}_2\text{O}_3\text{(s)} + \text{CO(g)} \rightarrow \text{Fe(s)} + \text{CO}_2\text{(g)}$. Autonomous monitoring systems audit the reaction by verifying that atom counts satisfy the law of conservation of mass. When this chemical equation is balanced using the lowest whole-number coefficients, what is the total number of individual atoms represented on the reactant side?

   • A) 11
   • B) 8
   • C) 9
   • D) 14
2. 2.

   A subterranean bio-mining colony cultivates specialized lithotrophic bacteria to extract metals from galena ore via an acid-leaching pathway represented by the balanced chemical equation: $3\text{PbS(s)} + 8\text{HNO}_3\text{(aq)} \rightarrow 3\text{Pb(NO}_3)_2\text{(aq)} + 3\text{S(s)} + 2X\text{(g)} + 4\text{H}_2\text{O(l)}$. Life-support environmental sensors must be calibrated to scrub the gaseous effluent $X$ released by this bioprocess. According to the conservation of mass in balanced chemical equations, what is the chemical formula of species $X$?

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

   Inside a sealed lunar botanical habitat, an autonomous life-support scrubber converts carbon dioxide exhaled by research personnel into breathable oxygen using solid potassium superoxide canisters. The gas exchange is governed by the unbalanced chemical equation: $\text{KO}_2\text{(s)} + \text{CO}_2\text{(g)} \rightarrow \text{K}_2\text{CO}_3\text{(s)} + \text{O}_2\text{(g)}$. When this equation is balanced using the lowest whole-number coefficients, what is the stoichiometric mole ratio of carbon dioxide absorbed to oxygen gas released ($\text{CO}_2 : \text{O}_2$)?

   • A) $1 : 1$
   • B) $1 : 2$
   • C) $4 : 3$
   • D) $2 : 3$
4. 4.

   To illuminate abyssal trenches, deep-sea exploration probes deploy automated flares powered by the rapid hydrolysis of calcium phosphide according to the unbalanced equation: $\text{Ca}_3\text{P}_2\text{(s)} + \text{H}_2\text{O(l)} \rightarrow \text{Ca(OH)}_2\text{(aq)} + \text{PH}_3\text{(g)}$. When this chemical equation is balanced using the lowest whole-number coefficients, what are the stoichiometric coefficients of $\text{H}_2\text{O(l)}$ and $\text{PH}_3\text{(g)}$, respectively?

   • A) 3 and 1
   • B) 4 and 2
   • C) 6 and 2
   • D) 6 and 1
5. 5.

   During a deep-space expedition, an automated atmospheric processor neutralizes hazardous silane gas by reacting it with dinitrogen monoxide propellant according to the unbalanced chemical equation: $\text{SiH}_4\text{(g)} + \text{N}_2\text{O(g)} \rightarrow \text{SiO}_2\text{(s)} + \text{N}_2\text{(g)} + \text{H}_2\text{O(g)}$. Technicians need to calibrate the reactant injection pumps using the stoichiometric ratios of the balanced reaction. When this chemical equation is balanced using the lowest whole-number coefficients, what is the sum of all stoichiometric coefficients in the reaction?

   • A) 12
   • B) 10
   • C) 8
   • D) 14

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