Chemical equations Transitional Reasoning Download PDF

Questions

1. 1.

   In the Ostwald process for nitric acid manufacturing, ammonia is oxidized according to the unbalanced equation $a\,\text{NH}_3\text{(g)} + b\,\text{O}_2\text{(g)} \rightarrow c\,\text{NO(g)} + d\,\text{H}_2\text{O(g)}$, where $a$, $b$, $c$, and $d$ represent the smallest possible whole-number stoichiometric coefficients. In a test run, an engineer introduces 12.0 moles of ammonia into the reactor alongside the exact stoichiometric quantity of oxygen gas needed for complete consumption. Which statement correctly identifies the sum of the stoichiometric coefficients in the balanced equation and the amount of oxygen gas consumed?

   • A) The sum of the coefficients $(a + b + c + d)$ is 19, and 15.0 moles of $\text{O}_2\text{(g)}$ are consumed.
   • B) The sum of the coefficients $(a + b + c + d)$ is 17, and 12.0 moles of $\text{O}_2\text{(g)}$ are consumed.
   • C) The sum of the coefficients $(a + b + c + d)$ is 19, and 9.6 moles of $\text{O}_2\text{(g)}$ are consumed.
   • D) The sum of the coefficients $(a + b + c + d)$ is 15, and 15.0 moles of $\text{O}_2\text{(g)}$ are consumed.
2. 2.

   An environmental chemist analyzes the complete combustion of an unknown gaseous hydrocarbon fuel, $C_xH_y$, according to the unbalanced equation $C_xH_y\text{(g)} + \text{O}_2\text{(g)} \rightarrow \text{CO}_2\text{(g)} + \text{H}_2\text{O(g)}$. In a controlled reaction, the complete combustion of exactly 1.0 mol of this hydrocarbon consumes 5.0 mol of $\text{O}_2\text{(g)}$ and produces 3.0 mol of $\text{CO}_2\text{(g)}$ along with water vapor. Based on the conservation of mass and atoms represented by balanced chemical equations, what is the molecular formula of the hydrocarbon and the stoichiometric coefficient of $\text{H}_2\text{O(g)}$ in the balanced equation?

   • A) The molecular formula is $C_3H_8$ and the coefficient of $\text{H}_2\text{O(g)}$ is 4.
   • B) The molecular formula is $C_3H_4$ and the coefficient of $\text{H}_2\text{O(g)}$ is 2.
   • C) The molecular formula is $C_3H_6$ and the coefficient of $\text{H}_2\text{O(g)}$ is 3.
   • D) The molecular formula is $C_2H_6$ and the coefficient of $\text{H}_2\text{O(g)}$ is 4.
3. 3.

   A chemist investigates the thermal decomposition of solid ammonium dichromate, represented by the unbalanced equation $\text{(NH}_4$_2\text{Cr}_2\text{O}_7$\text{(s)}$ \rightarrow \text{Cr}_2\text{O}_3$\text{(s)}$ + \text{N}_2$\text{(g)}$ + \text{H}_2\text{O(g)}\). During an experiment in an inert closed container, exactly 0.50 mol of ammonium dichromate decomposes completely. Based on the balanced chemical equation, which statement correctly identifies the stoichiometric coefficient of water vapor and the amounts of gases produced?

   • A) The stoichiometric coefficient of $\text{H}_2\text{O}$ is 2, and the decomposition produces 0.50 mol of $\text{N}_2$ and 1.0 mol of $\text{H}_2\text{O}$.
   • B) The stoichiometric coefficient of $\text{H}_2\text{O}$ is 2, and the decomposition produces 1.0 mol of $\text{N}_2$ and 2.0 mol of $\text{H}_2\text{O}$.
   • C) The stoichiometric coefficient of $\text{H}_2\text{O}$ is 4, and the decomposition produces 1.0 mol of $\text{N}_2$ and 4.0 mol of $\text{H}_2\text{O}$.
   • D) The stoichiometric coefficient of $\text{H}_2\text{O}$ is 4, and the decomposition produces 0.50 mol of $\text{N}_2$ and 2.0 mol of $\text{H}_2\text{O}$.
4. 4.

   A sealed container is charged with 6.0 moles of nitrogen gas and 12.0 moles of hydrogen gas. The gases react at elevated temperature and pressure according to the balanced equation $\text{N}_2\text{(g)} + 3\text{H}_2\text{(g)} \rightarrow 2\text{NH}_3\text{(g)}$. If the reaction proceeds until 8.0 moles of ammonia are produced, what is the total number of moles of gas present in the container?

   • A) 10.0 moles
   • B) 14.0 moles
   • C) 8.0 moles
   • D) 2.0 moles
5. 5.

   A chemical engineer investigates the reduction of iron(III) oxide by carbon monoxide in a blast furnace, represented by the unbalanced equation $\text{Fe}_2\text{O}_3\text{(s)} + \text{CO(g)} \rightarrow \text{Fe(s)} + \text{CO}_2\text{(g)}$. In an experiment, 2.0 moles of iron(III) oxide react completely with the required amount of carbon monoxide. Which statement correctly describes the mole quantities of reactants consumed and products formed based on the balanced equation?

   • A) The reaction consumes 2.0 moles of carbon monoxide to produce 2.0 moles of iron and 3.0 moles of carbon dioxide.
   • B) The reaction consumes 3.0 moles of carbon monoxide to produce 2.0 moles of iron and 3.0 moles of carbon dioxide.
   • C) The reaction consumes 6.0 moles of carbon monoxide to produce 4.0 moles of iron and 6.0 moles of carbon dioxide.
   • D) The reaction consumes 6.0 moles of carbon monoxide to produce 2.0 moles of iron and 3.0 moles of carbon dioxide.