To determine which hydroxide is amphoteric, we need to understand what amphoteric substances are. An amphoteric hydroxide is one that can act as both an acid and a base. In other words, it can react with both acids and bases.
Understanding Each Option:
$\ce{Ca(OH)2}$: Calcium hydroxide is a strong base and typically does not exhibit amphoteric properties.
$\ce{Be(OH)2}$: Beryllium hydroxide is known to be amphoteric because it can react with acids to form salts and with bases to form complex beryllate ions.
$\ce{Sr(OH)2}$: Strontium hydroxide is similar to other group 2 hydroxides like calcium hydroxide, behaving as a strong base rather than an amphoteric compound.
$\ce{Mg(OH)2}$: Magnesium hydroxide, while somewhat less reactive than calcium hydroxide, primarily acts as a base.
Conclusion: From the explanations above, $\ce{Be(OH)2}$ is the compound that fits the definition of an amphoteric hydroxide, as it has the ability to react with both acids and bases.
