חַ
When "Cha" becomes "Ach"
(Chet + Patach)
When חַ is at the end of a word, it has a sound of ach instead of cha. This is a kind of weird exception which is why it's not hard to remember. The key is to just practice with a few words so it feels natural.
Reading Practice
בּוֹטֵחַ Boteach Trusts.
כֹּחַ Koach Strength.
לַנוּחַ Lanuach To rest.
לוּחַ Luach Calendar or board.
מִזבֵּחַ Mizbeach Altar.
מוֹחַ Moach Brain.
נוֹחַ Noach Noah.
Let's move on to another letter...