Great question! In many English words, "ch" is pronounced as K. This is only true in some words. These words usually come from the Greek language originally (psychology, echo, chemistry, etc.) Most of the time, the "ch" has a softer sound like an "sh" but with a T in front: "tsh." (chat, chance, sandwich).

And it’s the same in french: écho, psychologie, chaos, chlore, chœur, choléra, chrétien, chrome, chronique, chrysalide, etc. Same reason: from the Greek language.

Or chorus.

The h is silent. There are few words like this...normally scientific: e.g. chelate