Arrange the given compounds based on their relative Brønsted acidities.

Arrange the given compounds based on their relative Brønsted acidities. Strongest Brønsted acid H-Br H-OH H-NH2 H-F H-CH3 Weakest Brønsted acid

The Correct Answer and Explanation is:

Correct Order of Brønsted Acidity (Strongest to Weakest):

HBr > HF > H2O > NH3 > CH4

Now, match this with the given compounds:
H–Br > H–F > H–OH > H–NH2 > H–CH3

Explanation

Brønsted acids are substances that donate protons (H⁺ ions). The strength of a Brønsted acid depends on how easily it can donate this proton. This is influenced by several factors including bond strength, electronegativity of the bonded atom, and the stability of the conjugate base formed after deprotonation.

Let us analyze the compounds in the list:

1. H–Br (Hydrobromic acid)
   This is a strong acid. The H–Br bond is weak and easily broken, and the Br⁻ ion is very stable due to its large size and ability to disperse negative charge. Therefore, H–Br donates protons easily.
2. H–F (Hydrofluoric acid)
   Although fluorine is very electronegative, the H–F bond is extremely strong. This makes HF less willing to donate a proton than HBr. However, HF is still more acidic than water due to the high electronegativity of fluorine stabilizing the resulting F⁻ ion.
3. H–OH (Water)
   Water is a very weak acid. It can donate a proton to form OH⁻, but this does not happen easily compared to strong acids. The oxygen in OH⁻ is electronegative and can stabilize the negative charge, but not as effectively as halide ions.
4. H–NH2 (Ammonia)
   The nitrogen atom is less electronegative than oxygen and halogens, making the NH2⁻ conjugate base less stable. As a result, ammonia is a weaker acid than water.
5. H–CH3 (Methane)
   Methane is an extremely weak acid. Carbon is not electronegative enough to stabilize a negative charge, and the C–H bond is very strong. The CH3⁻ ion is highly unstable, making methane essentially non-acidic.

In summary, acid strength generally increases as the stability of the conjugate base increases and the bond holding the proton becomes weaker. This explains the ranking:
HBr > HF > H2O > NH3 > CH4.