1 mole of water = 18 grams (you can find this by finding mass of two hydrogen and one oxygen which is (1*2) + 16 = 18)
1.8 grams = 0.1 moles
1 H2O molecule has 10 electrons so 0.1 moles can be computed as:
(6.023*10^23)*(0.1)*10 = 6.023*10^23 electrons
No you couldn’t, because a drop of water has approximately 1.61*10^21 molecules, so this would be slightly more than a drop of water
The third is one: controlled burn
35g Mg x 1mol / 24g = 840 mol