What is the significance of 10H2O in washing soda?
Answers
Explanation:
Some compounds (particularly ionic compounds) have water trapped within the lattice when they crystallize out of solution. This doesn’t make the compound wet to the touch, but it does mean that it’s possible to get water from the compound—usually by heating it and collecting the water in a condenser off to the side. The 10H2O in this particular example simply means that for every two sodium ions and one carbonate ion, there are ten water molecules trapped in the lattice.
It’s especially important to know about these spare water molecules if you’re trying to create a solution of a particular concentration, since you’re going to be weighing out the crystals rather than counting up sodium ions and dividing by two. A hundred grams of Na2CO3 is going to get you a much more concentrated solution than a hundred grams of Na2CO3.10H2O.
As a side note, I’ve always found one of the names for this phenomenon (waters of hydration) to be remarkably redundant