Final answer:
The mole ratio of salt to water in Na2SO4.10H2O is 1:10.
Step-by-step explanation:
This means that for every one mole of Na2SO4, there are 10 moles of water molecules.
The formula Na2SO4·10H2O indicates that there are 10 water molecules attached to each Na2SO4 unit.
In other words, the compound contains 1 mole of salt (Na2SO4) and 10 moles of water (H2O).
So therefore the mole ratio of salt to water in the compound Na2SO4·10H2O is 1:10.