Which molecule is amphoteric?

A.
NH4+

B.
H2O

C.
H2CO3−

D.
H2SO4

Agas has a volume of 0.7 l at 300 mmhg. what would be the new volume at 900 mmhg

According to each substances heat of fusion, which of the items below requires more heat to be added per gram of substance to go from solid to liquid? silver sulfur water lead

Consider hydrogen in an excited state n = 5n=5 that emits photons to reach the ground state. there are various possible transitions other than straight to the ground state that can occur; for example, it can drop to the n = 3n=3 state followed by the n = 3n=3 to the ground state transition. which of the possible transitions will result in the emission of a photon in the visible region?