To determine which substance has the highest boiling point among HF (hydrofluoric acid), [tex]\( H_2O \)[/tex] (water), [tex]\( Na_2S \)[/tex] (sodium sulfide), and [tex]\( NH_3 \)[/tex] (ammonia), we compare the boiling points of each:
1. Boiling point of HF (hydrofluoric acid): 19.5°C
2. Boiling point of [tex]\( H_2O \)[/tex] (water): 100.0°C
3. Boiling point of [tex]\( Na_2S \)[/tex] (sodium sulfide): 920.0°C
4. Boiling point of [tex]\( NH_3 \)[/tex] (ammonia): -33.34°C
Next, we identify the highest value among these boiling points:
- HF: 19.5°C
- [tex]\( H_2O \)[/tex]: 100.0°C
- [tex]\( Na_2S \)[/tex]: 920.0°C
- [tex]\( NH_3 \)[/tex]: -33.34°C
From the given values, the highest boiling point is 920.0°C, which corresponds to [tex]\( Na_2S \)[/tex] (sodium sulfide).
Therefore, among HF, [tex]\( H_2O \)[/tex], [tex]\( Na_2S \)[/tex], and [tex]\( NH_3 \)[/tex], the substance with the highest boiling point is [tex]\( Na_2S \)[/tex].
