Question

what does 10h2O signify in washing soda?Does it make Na2co3 wet?

Answer 1

10H₂O is the water molecules of crystallisation.....

It just signifies the deliquescent property of it.
Not that it makes it wet, it tells that the crystals are not completely dry and contain some moisture

Answer 2

Explanation:

The formula of washing soda is $Na_{2}CO_{3}.10H_{2}O$. The $10H_{2}O$ represents that there are ten water molecules attached as a single unit with sodium carbonate that is $Na_{2}CO_{3}$.

The presence of ten water molecules make it washing soda otherwise it is only burnt soda ash.

No, $10H_{2}O$ does not make washing soda wet as it only represents the units attached to the sodium carbonate.