Which of the following acids would be classified as the strongest?

• A. CH₄
• B. NH₃
• C. H₂O
• D. HF
• E. PH₃

Answer: (D)

Verified step by step guidance

1. Identify the type of acids in the list. CH4, NH3, H2O, HF, and PH3 are all binary compounds, but only HF is a hydrogen halide, which is typically a strong acid.
2. Understand the concept of acid strength. Acid strength is determined by the ability of the acid to donate a proton (H+). Strong acids completely dissociate in water, while weak acids do not.
3. Consider the electronegativity of the atoms bonded to hydrogen. The more electronegative the atom, the stronger the acid. Fluorine (in HF) is the most electronegative element, making HF a strong acid.
4. Evaluate the bond strength between hydrogen and the other atom in the molecule. A weaker bond means the acid can more easily donate a proton. The H-F bond is weaker compared to the bonds in CH4, NH3, H2O, and PH3, facilitating proton donation.
5. Conclude that HF is the strongest acid among the given options due to its high electronegativity and relatively weaker bond strength, allowing it to dissociate more completely in water.