Chemical equations Knowledge-Based Download PDF

Questions

1. 1.

   In a chemical equation, what is the fundamental difference between the notations $\text{NaCl}(l)$ and $\text{NaCl}(aq)$?

   • A) $\text{NaCl}(l)$ denotes pure liquid sodium chloride at or above its melting point, whereas $\text{NaCl}(aq)$ denotes sodium chloride dissolved in liquid water.
   • B) $\text{NaCl}(l)$ denotes an aqueous solution of sodium chloride, whereas $\text{NaCl}(aq)$ denotes solid sodium chloride suspended in water.
   • C) $\text{NaCl}(l)$ denotes sodium chloride dissolved in an organic solvent, whereas $\text{NaCl}(aq)$ denotes molten sodium chloride.
   • D) $\text{NaCl}(l)$ denotes hydrated sodium chloride crystals, whereas $\text{NaCl}(aq)$ denotes anhydrous gaseous sodium chloride.
2. 2.

   Why must stoichiometric coefficients, rather than subscripts within chemical formulas, be adjusted when balancing a chemical equation?

   • A) Adjusting subscripts changes the physical states of the substances participating in the reaction.
   • B) Adjusting subscripts alters the overall rate and activation energy required for the chemical reaction.
   • C) Adjusting subscripts destroys existing atoms, which directly violates the law of conservation of mass.
   • D) Adjusting subscripts changes the chemical identity and atomic composition of the compounds involved.
3. 3.

   Based on the balanced chemical equation $2\text{C}_2\text{H}_6(g) + 7\text{O}_2(g) \rightarrow 4\text{CO}_2(g) + 6\text{H}_2\text{O}(g)$, what is the mole ratio of oxygen gas consumed to carbon dioxide produced?

   • A) 7 : 4
   • B) 4 : 7
   • C) 7 : 2
   • D) 1 : 2
4. 4.

   Which quantity is always conserved between the reactants and products in every balanced chemical equation?

   • A) Total number of molecules
   • B) Total number of moles of substances
   • C) Total volume of gases under standard conditions
   • D) Total number of atoms of each element
5. 5.

   When the chemical equation $\text{Al} + \text{H}_2\text{SO}_4 \rightarrow \text{Al}_2(\text{SO}_4)_3 + \text{H}_2$ is balanced using the smallest whole-number coefficients, what is the sum of all stoichiometric coefficients?

   • A) 9
   • B) 8
   • C) 7
   • D) 6