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Question 10.18: Predict whether the following salts produce an acidic, basic...

Predict whether the following salts produce an acidic, basic, or neutral solution:
(a) BaCl_2           (b) NaCN           (c) NH_4NO_3
ANALYSIS Look in Table 10.1 (p. 300) to see the classification of acids and bases as strong or weak.

 

CONJUGATE BASE ACID
Increasing base strength \left. \begin{matrix} ClO_4  ^- & Perchlorate  ion \\ HSO_4  ^- & Hydrogen \\ &     sulfate  ion \\ I^- & Iodide  ion \\ Br^- & Bromide  ion \\ Cl^- & Chloride  ion \\ NO_3  ^- & Nitrate  ion \end{matrix} \right\} \pmb{Little or no reaction as bases} \pmb{Strong  acids:  100\%  dissociated} \begin{cases} Perchloric  acid  & HClO_4 \\ Sulfuric  acid & H_2SO_4 \\ \\ Hydriodic  acid & HI \\ Hydrobromic  acid & HBr \\ Hydrochloric  acid & HCl \\ Nitric  acid & HNO_3 \end{cases}
\pmb{ H_2O }                  \pmb{ Water } \pmb{ Hydronium  ion }          \pmb{ H_3O^+ }
\left. \begin{matrix} SO_4  ^{2-} & Sulfate  ion \\   \\  H_2PO_4  ^- & Dihydrogen \\ &    phosphate  ion \\ NO_2  ^- & Nitrite  ion \\ F^- & Fluoride  ion \\ CH_3COO^- & Acetate  ion \end{matrix} \right\} \pmb{Very  weak  bases} \pmb{Weak  acids} \begin{cases} Hydrogen  & HSO_4  ^- \\       sulfate  ion \\ Phosphoric  acid & H_3PO_4 \\ \\ Nitrous  acid & HNO_2 \\ Hydrofluoric  acid & HF \\ Acetic  acid & CH_3COOH \end{cases}
\left. \begin{matrix} HCO_3  ^- & Bicarbonate  ion \\ HPO_4  ^{2-} & Hydrogen \\ &          phosphate ion \\ NH_3 & Ammonia \\ CN^- & Cyanide  ion \\ CO_3  ^{2- } & Carbonate  ion \\ PO_4  ^{3-} & Phosphate  ion  \\  \end{matrix} \right\} \pmb{Weak  bases} \pmb{Very  weak  acids} \begin{cases} Carbonic  acid & H_2CO_3 \\ Dihydrogen & H_2PO_4  ^- \\    phosphate  ion \\ Ammonium  ion & NH_4  ^+ \\ Hydrocyanic  acid & HCN  \\ Bicarbonate  ion & HCO_3  ^- \\ Hydrogen & HPO_4  ^{2-} \\    phosphate  ion \end{cases}
\left. \pmb{ OH^- }           \pmb{ Hydroxide ion }      \right\} \pmb{   Strong base} \pmb{ Water   }                      \pmb{ H_2O }
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(a) BaCl_2 gives a neutral solution because it is formed from a strong acid (HCl) and a strong base \left[ Ba(OH)_2 \right] .
(b) NaCN gives a basic solution because it is formed from a weak acid (HCN) and a strong base (NaOH).
(c) NH_4NO_3 gives an acidic solution because it is formed from a strong acid (HNO_3) and a weak base NH_3.

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