12 moles are in the 175L of SO2 gas at STP
They are too small to see with the naked eye
This sounds good so far.
May want to check how you say "and are spread way out" - a better way to say it would be "the crystals are spread out"
since the unit for the heat of fusion is kJ/mol, you're going to have to convert the grams into moles in order to cancel out the unit. After that, you can solve like normal.