Question

In washing soda ie. Na2Co3.10H2O. Does 10H2O make Na2Co3 wet?

Answer 1

No. The "." represents that the H2O molecules have bonded with the Na2Co3 molecules. So, it doesn't make it wet.

Answer 2

Explanation:

The presence of $10H_{2}O$ in $Na_{2}CO_{3}.10H_{2}O$ is known as water of crystallization. It does not make sodium carbonate wet but it depicts that ten units of water molecules are attached to the sodium carbonate.  

These water of crystallization are locked up in sodium carbonate molecule.

Washing soda is a dry compound and has white color.