alleryStart learning →Carbon dioxide dissolved in aqueous sodium hydroxide gives aqueous sodium carbonate and water. Which ion is the spectator?
AHydroxide ion, OH-
BSodium ion, Na+
CCarbonate ion, CO32-
DHydrogen ion, H+
Answer & Solution
Correct answer: B. Sodium ion, Na+
1. The molecular equation is CO2(aq) + 2NaOH(aq) giving Na2CO3(aq) + H2O(l).
2. Both NaOH and Na2CO3 are dissolved ionic compounds, so write them as ions.
3. The left side then holds CO2, 2 Na+ and 2 OH-; the right side holds 2 Na+, CO32- and H2O.
4. Sodium ions appear as 2 Na+ on both sides, unchanged, so Na+ is the spectator.
5. Hydroxide is consumed, so it is not a spectator.
6. Carbonate is produced, so it is not a spectator either.
7. Free H+ never appears in this equation, so that option describes nothing present.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 4 "Stoichiometry of Chemical Reactions", section 4.1 Writing and Balancing Chemical Equations_
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