Chemical equations Original Scenario-Based Download PDF

Questions

1. 1.

   Aboard the deep-space research vessel Aethelgard, environmental engineers purify reclaimed wastewater contaminated with soluble barium ions by treating the stream with sodium sulfate. The process forms an insoluble barium sulfate precipitate alongside dissolved sodium chloride, initially recorded as the molecular equation $\text{BaCl}_2(aq) + \text{Na}_2\text{SO}_4(aq) \rightarrow \text{BaSO}_4(s) + 2\text{NaCl}(aq)$. To track only the chemical species undergoing actual chemical change, the environmental monitoring system requires the net ionic equation. Which chemical equation correctly represents the net ionic equation for this process?

   • A) $\text{BaCl}_2(aq) + \text{Na}_2\text{SO}_4(aq) \rightarrow \text{BaSO}_4(s) + 2\text{NaCl}(aq)$
   • B) $\text{Ba}^{2+}(aq) + 2\text{Cl}^-(aq) + 2\text{Na}^+(aq) + \text{SO}_4^{2-}(aq) \rightarrow \text{BaSO}_4(s) + 2\text{Na}^+(aq) + 2\text{Cl}^-(aq)$
   • C) $\text{Ba}^{2+}(aq) + \text{SO}_4^{2-}(aq) \rightarrow \text{BaSO}_4(s)$
   • D) $\text{Na}^+(aq) + \text{Cl}^-(aq) \rightarrow \text{NaCl}(aq)$
2. 2.

   Aboard an orbital research station, an automated atmospheric incinerator decomposes an unknown synthetic coolant vapor, designated compound $X$, by reacting it with oxygen. The process is governed by the balanced chemical equation $2X(g) + 13\text{O}_2(g) \rightarrow 8\text{CO}_2(g) + 10\text{H}_2\text{O}(g) + 2\text{SiO}_2(s)$. Based on the law of conservation of mass and atom balancing in chemical equations, what is the molecular formula of compound $X$?

   • A) $\text{C}_4\text{H}_{10}\text{SiO}_2$
   • B) $\text{C}_8\text{H}_{20}\text{Si}_2\text{O}_4$
   • C) $\text{C}_4\text{H}_{10}\text{Si}$
   • D) $\text{C}_4\text{H}_5\text{SiO}$
3. 3.

   To revitalize depleted hydroponic beds inside the orbital greenhouse of an interstellar ark, botanists synthesize ammonium sulfate fertilizer by injecting ammonia gas into a mist of aqueous sulfuric acid. Which balanced chemical equation accurately represents this process while respecting the law of conservation of mass?

   • A) $\text{NH}_3(g) + \text{H}_2\text{SO}_4(aq) \rightarrow \text{NH}_5\text{SO}_4(aq)$
   • B) $\text{N}_2\text{H}_6(g) + \text{H}_2\text{SO}_4(aq) \rightarrow (\text{NH}_4)_2\text{SO}_4(aq)$
   • C) $\text{NH}_3(g) + \text{H}_2\text{SO}_4(aq) \rightarrow (\text{NH}_4)_2\text{SO}_4(aq)$
   • D) $2\text{NH}_3(g) + \text{H}_2\text{SO}_4(aq) \rightarrow (\text{NH}_4)_2\text{SO}_4(aq)$
4. 4.

   In a sealed Martian outpost, life-support engineers operate a Sabatier reactor that recycles carbon dioxide exhaled by the crew into methane and water vapor according to the balanced equation $\text{CO}_2(g) + 4\text{H}_2(g) \rightarrow \text{CH}_4(g) + 2\text{H}_2\text{O}(g)$. Based on this chemical equation, which statement correctly describes the quantitative relationships between the reactants and products?

   • A) Exactly 1 gram of $\text{CO}_2$ reacts completely with 4 grams of $\text{H}_2$ to yield 1 gram of $\text{CH}_4$ and 2 grams of $\text{H}_2\text{O}$.
   • B) The total number of moles of gas is conserved because the total mass of the closed system remains constant.
   • C) Every 1 mole of $\text{CO}_2$ consumed requires 4 moles of $\text{H}_2$ and yields exactly 2 moles of $\text{H}_2\text{O}$ vapor.
   • D) The mass of $\text{CH}_4$ generated is always half the mass of $\text{H}_2\text{O}$ generated because of their 1:2 coefficient ratio.
5. 5.

   To prevent toxic gas accumulation inside the submerged habitat of Mariana Station, an automated catalytic scrubber neutralizes hydrogen sulfide by reacting it with sulfur dioxide gas to yield solid elemental sulfur and water vapor. The process is represented by the unbalanced chemical equation $a\text{H}_2\text{S} + b\text{SO}_2 \rightarrow c\text{S} + d\text{H}_2\text{O}$. Which set of stoichiometric coefficients balances the equation using the lowest whole-number ratio?

   • A) a = 1, b = 2, c = 3, d = 2
   • B) a = 2, b = 2, c = 4, d = 2
   • C) a = 3, b = 1, c = 4, d = 3
   • D) a = 2, b = 1, c = 3, d = 2