How many molecules of water...

Question

Called the water of hydration, surround each molecule of sodium carbonate decahydrate, Na2CO3 . 10H2O?

And calculate the molar mass of sodium carbonate decahydrate.

Answer 1

The molecular formula tells you how many water molecules are associated with each molecular of sodium carbonate - the "10 H₂O" is the hydration sphere. There are 10 water molecules per sodium carbonate.

The molecular weight of the deachydrate is the molecular weight of Na₂CO₃ added to the molecular weight of the 10 H₂O.

Na: 2 x 23 = 46 g/mol

C: 1 x 12 = 12 g/mol

O: 3 x 16 = 48 g/mol

H₂O: 10 x 18 = 180 g/mol

Add these together: 286 g/mol is the molecular weight.