Question

Write formulas for two salts that (a) contain \(\mathrm{NH}_{4}^{+}\) and are basic. (b) contain \(\mathrm{CO}_{3}^{2-}\) and are basic. (c) contain \(\mathrm{Br}^{-}\) and are neutral. (d) contain \(\mathrm{CrO}_{4}^{2-}\) and are acidic.

Short answer

Question: Create salts with the following properties: (a) Contains the ammonium ion and has a basic property. (b) Contains the carbonate ion and has a basic property. (c) Contains the bromide ion and has a neutral property. (d) Contains the chromate ion and has an acidic property. Answer: (a) Ammonium acetate (\(\mathrm{NH}_{4}\mathrm{CH}_{3}\mathrm{COO}\)) (b) Sodium carbonate (\(\mathrm{Na}_{2}\mathrm{CO}_{3}\)) or Potassium carbonate (\(\mathrm{K}_{2}\mathrm{CO}_{3}\)) (c) Sodium bromide (\(\mathrm{NaBr}\)) (d) Aluminum chromate (\(\mathrm{Al}_{2}(\mathrm{CrO}_{4})_{3}\))

Step-by-step solution

(a) Salt with Ammonium and Basic Property

To find a basic salt containing the \(\mathrm{NH}_{4}^{+}\) ion, we should look for an anion that comes from a weak acid. Weak acid anions will be more likely to gain a proton (H+), making the resulting solution basic. Let's pick the acetate ion \((\mathrm{CH}_{3}\mathrm{COO}^{-})\), which is the conjugate base of acetic acid (a weak acid). Forming a salt with ammonium, we get: \(\mathrm{NH}_{4}\mathrm{CH}_{3}\mathrm{COO}\) (Ammonium acetate)

(b) Salt with Carbonate and Basic Property

We are given that the salt contains the carbonate ion \((\mathrm{CO}_{3}^{2-})\) and should be basic. To find such a salt, the cation should not produce acidic solutions in water. An example of such cations are alkali metals like sodium (Na+) and potassium (K+), because they do not affect the pH. Forming salts with carbonate, we can have: \(\mathrm{Na}_{2}\mathrm{CO}_{3}\) (Sodium carbonate) \(\mathrm{K}_{2}\mathrm{CO}_{3}\) (Potassium carbonate)

(c) Salt with Bromide and Neutral Property

We want a salt that is neutral and contains bromide ion \((\mathrm{Br}^{-})\). To get a neutral salt, both the cation and anion should not affect the pH of the solution when dissolved in water. An example is taking a salt of a strong acid and strong base. The hydrobromic acid (strong acid) contains the bromide ion, and sodium hydroxide (strong base) contains sodium ion. Forming a salt with these ions, we get: \(\mathrm{NaBr}\) (Sodium bromide)

(d) Salt with Chromate and Acidic Property

We want a salt that is acidic and contains the chromate ion \((\mathrm{CrO}_{4}^{2-})\). For a salt to be acidic, the cation should come from a weak base which will protonate the ion, shifting the pH to the acidic side. Conjugate acids of weak bases can be good candidates. The aluminum ion (\(\mathrm{Al}^{3+}\)) is an example of such a cation since it has a weak base conjugate (aluminum hydroxide). Forming a salt with chromate, we get: \(\mathrm{Al}_{2}(\mathrm{CrO}_{4})_{3}\) (Aluminum chromate)