What is the product formed when you mix 2-ethyl-3-methylpentanoic acid, and 2-propanol?

The products formed are 2-propyl 2-ethyl-3-methylpentanoic acid and water.
CH₃CH₂CH(CH₃)CH(C₂H₅)COOH + CH₃CH₂OH → CH₃CH₂CH(CH₃)CH(C₂H₅)COOCH₂CH₃ + H₂O

However, the reaction is very slow at room temperature and in the absence of catalyst.
At higher temperature and in the presence of concentrated sulfuric acid as catalyst, the reaction becomes much faster.

Mixing them will just give the mixture. There will be no reaction. To get an ester (Isopropyl 2-ethyl-3-methylpentanoate) you must employ a strong acid catalyst. Heating will really help too.