Which substance is a base? HCOOH RbOH H2CO3 NaNO3
The correct answer and explanation is:
The substance that is a base among the options is RbOH (rubidium hydroxide).
Explanation (Approx. 300 words):
In chemistry, substances are classified as acids, bases, or salts based on their behavior in water, particularly in relation to the concentration of hydrogen ions (H⁺) and hydroxide ions (OH⁻) they produce.
1. RbOH (Rubidium Hydroxide) – Base ✅
RbOH is a strong base. It is an alkali metal hydroxide, and like other Group 1 metal hydroxides (e.g., NaOH, KOH), it dissociates completely in water to produce Rb⁺ and OH⁻ ions: RbOH→Rb++OH−\text{RbOH} \rightarrow \text{Rb}^+ + \text{OH}^-
The presence of OH⁻ ions makes it basic. It increases the pH of a solution and can neutralize acids.
2. HCOOH (Formic Acid) – Acid
Formic acid is a weak acid. It only partially ionizes in water: HCOOH⇌H++HCOO−\text{HCOOH} \rightleftharpoons \text{H}^+ + \text{HCOO}^-
It donates protons (H⁺), which is characteristic of acids.
3. H₂CO₃ (Carbonic Acid) – Acid
Carbonic acid is also a weak acid, formed when carbon dioxide dissolves in water: H2CO3⇌H++HCO3−\text{H}_2\text{CO}_3 \rightleftharpoons \text{H}^+ + \text{HCO}_3^-
It dissociates to release hydrogen ions, lowering the pH.
4. NaNO₃ (Sodium Nitrate) – Salt
Sodium nitrate is a neutral salt formed from the reaction of a strong base (NaOH) and a strong acid (HNO₃). It does not act as an acid or base in solution. It dissociates into Na⁺ and NO₃⁻ ions, neither of which affects the pH significantly.
Conclusion:
Among the given options, RbOH is the only base. It produces hydroxide ions in solution and is classified as a strong base due to its complete dissociation.