When does Chloe find out Clark's secret in Smallville?

Answer 1

Chloe finds out about Clark's powers in the Season 4 episode that is titled "Pariah" however she finds out about his alien background in the Season 5 premiere episode that is titled "Arrival."

Answer 2

Chloe Sullivan finds out about Clark's superhuman powers due to a Kryptonite-infected person named Alicia Baker exposing him to her however she learns about his heat vision and X-ray vision in the episode that is titled "Blank" and she learns about his weakness to meteor rocks (also called Kryptonite) in the episode that is titled "Spirit" however she does not find out about him being an alien until the Season 5 premiere episode that is titled "Arrival."

Answer 3

Yes Chloe found out about Clark's superhuman abilities such as super strength and super speed in the Season 4 episode titled "Phariah," she later found out in following episodes titled "Spirit" that he had a strange weakness around meteor rocks and in "Blank" she finds out about his X-Ray and heat vision powers. In the 4th season finale both are transported to the North and which was when the Fortress of Solitude was formed (the forming of it and everything in it happened in the 5th season premiere) and he began his training however she got too close to the training field which activated its defenses which led to her admitting to him that she knows about his powers at which point while they're alone in the Yukon hospital and he explains to her that the meteor rocks didn't give him his powers that he wasn't even born on Earth.

Answer 4

She actually finds out about it by herself in season 4 but he confirms it at the very beginning of season 5