Predict whether aqueous solutions of the following compounds are acidic, basic, or neutral. compound K Br KOH NH
NO
solution is…? acidic basic neutral acidic basic neutral acidic basic neutral
The Correct Answer and Explanation is:
Here are the correct predictions for the aqueous solutions of the given compounds:
- KBr: neutral
- KOH: basic
- NH₄NO₃: acidic
Now, let’s walk through why this is the case.
KBr is potassium bromide, a salt formed from a strong base (KOH) and a strong acid (HBr). When dissolved in water, it completely dissociates into K⁺ and Br⁻ ions. Neither of these ions reacts with water to change its pH, so the resulting solution remains neutral.
KOH, or potassium hydroxide, is a classic strong base. It fully dissociates in water to yield K⁺ and OH⁻ ions. The presence of OH⁻ ions increases the pH above 7, making the solution strongly basic.
NH₄NO₃, ammonium nitrate, is more nuanced. It is the salt of a weak base (NH₃, ammonia) and a strong acid (HNO₃, nitric acid). When NH₄NO₃ dissolves in water, it dissociates into NH₄⁺ and NO₃⁻. The NH₄⁺ ion can donate a proton to water, forming NH₃ and H₃O⁺. This reaction introduces extra hydrogen ions into the solution, reducing the pH and making the solution acidic. The NO₃⁻ ion, being the conjugate base of a strong acid, does not interact with water in a way that affects pH.
To sum it up: the behavior of a salt solution depends on the relative strengths of the parent acid and base from which it is derived. If both are strong, the solution is neutral. If the base is strong and the acid is weak, the solution is basic. If the base is weak and the acid is strong, the solution is acidic. This classification helps predict the chemical environment in which other reactions may take place.
