Is this chain solid silver or plated?

It is solid 925 sterling silver, with a rhodium electroplating on top for shine and tarnish resistance. The core metal is silver throughout.

Can I hang a pendant on it?

Yes, but keep the pendant small and light. The links are 0.7mm and the chain weighs about a gram, so a heavy pendant can stretch or break it.

Which length should I choose?

The 16-inch length sits close to the collarbone, while 18 inches rests a bit lower on the chest. Both lengths weigh almost the same, so the choice is about where you want the chain to fall.

Will the rhodium plating wear off?

Rhodium plating on fine chains can thin with daily friction, especially where a pendant rubs. The silver underneath is still sterling, so it stays wearable, but the bright white finish may dull over time.

How should I care for it?

Keep it away from perfume, chlorine and harsh cleaners, and wipe it with a soft cloth after wear. Store it flat or hanging to avoid kinks in the thin links.