Bond Angles in Tetrahedral Molecules

Steps:

• Ammonia (NH3) reacts with HCl to form NH4+, where N accepts H+ using its lone pair.
• NH3 has trigonal pyramidal shape with H-N-H angle ~107° due to lone pair repulsion.
• NH4+ has tetrahedral geometry with four N-H bonds, H-N-H angle 109.5°.
• Methane (CH4) also has tetrahedral geometry with H-C-H angle 109.5°.

Why D is correct:

• Both NH4+ and CH4 follow VSEPR theory for AX4 notation, yielding identical 109.5° bond angles.

Why the others are wrong:

• A: NH4+ is acidic, as it donates H+ (e.g., NH4+ ⇌ NH3 + H+).
• B: N in NH3 donates lone pair to H+ from HCl; H+ does not donate electrons.
• C: NH3 angle is 107° (lone pair distortion); NH4+ is 109.5° (no lone pairs).

Final answer: D