Answer
$HCl$ is stronger than $H_2S$ because, $S$ and $Cl$ are on the same row of the periodic table, and $Cl$ is more electronegative.
Work Step by Step
- The more electronegative element will attract the electrons from the hydrogen, making the donation easier. Therefore, increasing the acidity.**
** Only if you are comparing elements in the same row, because the size of the atom is a factor too.
