which of the following is a weak base? Why?
a. KOH b. NH4+ c. CH3 2- d. HF e. H3PO4
To determine which of the given options is a weak base, we need to understand the concept of weak bases and their properties.
A weak base is a substance that partially dissociates in water to produce hydroxide ions (OH-) but doesn't fully ionize. Weak bases have limited ability to accept protons (H+ ions).
Let's evaluate each option:
a. KOH: KOH is potassium hydroxide. It is a strong base because it completely dissociates in water to form potassium ions (K+) and hydroxide ions (OH-).
b. NH4+: NH4+ is ammonium. It is actually a cation or a positively charged ion and cannot act as a base on its own since it doesn't contain any hydroxide ions.
c. CH3 2-: CH3 2- is methyl anion. It doesn't contain any hydroxide ions, so it cannot act as a base.
d. HF: HF is hydrofluoric acid. While it is an acid, it can also act as a weak base. HF partially dissociates in water to produce fluoride ions (F-) and a few hydroxide ions (OH-). Hence, HF is a weak base.
e. H3PO4: H3PO4 is phosphoric acid. It is an acid and cannot function as a base.
Therefore, the weak base among the given options is HF (option d) because it partially dissociates in water to produce hydroxide ions.