Problem: Consider the following acid-neutralization reactions involving the strong base NaOH(aq):HNO3(aq) + NaOH(aq) → NaNO3(aq) + H2O(l)HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)NH4+(aq) + NaOH(aq) → NH3(aq) + Na+(aq) + H2O(l)In the third equation NH4+(aq) is acting as an acid. Based on the value of ΔH˚ for this reaction, do you think it is a strong or a weak acid?

FREE Expert Solution

ΔH°rxn=ΔH°f, prod-ΔH°f, react


HNO3(aq) + NaOH(aq) → NaNO3(aq) + H2O(l)

ΔH°rxn=(1 mol NaNO3)(-446.2 kJ1 mol NaNO3)+(1 mol H2O)-285.83 kJ1 mol H2O                      -(1 mol HNO3)(-206.6 kJ1 mol HNO3)+(1 mol NaOH)(-469.6 kJ1 mol NaOH)

ΔH°rxn = -55.83 kJ/mol


HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)

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Problem Details
Consider the following acid-neutralization reactions involving the strong base NaOH(aq):

HNO3(aq) + NaOH(aq) → NaNO3(aq) + H2O(l)
HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
NH4+(aq) + NaOH(aq) → NH3(aq) + Na+(aq) + H2O(l)

In the third equation NH4+(aq) is acting as an acid. Based on the value of ΔH˚ for this reaction, do you think it is a strong or a weak acid?

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