Just 2 valence electrons.
Hydrogen already has one to start with, as well. With the exception of hydrogen and helium, all other atoms need 8 valence e-
Answer:
9.82 g of Mg(NO₃)₂
Explanation:
Let's determine the reaction:
2AgNO₃ + MgBr₂ → Mg(NO₃)₂ + 2AgBr
2 moles of nitrate silver reacts with MgBr₂ in order to produce 1 mol of magnesium nitrate and silver bromide.
We determine the moles of AgNO₃
22.5 g . 1mol / 169.87g = 0.132 moles
Ratio is 2:1.
2 moles of silver nitrate can produce 1 mol of magnesium nitrate
Then, our 0.132 moles may produce (0.132 . 1)/ 2 = 0.0662 moles
We convert moles to mass:
0.0662 mol . 148.3 g/ mol = 9.82 g
The mass of the water is 1.20 - 0.80 = 0.40 grams.
The % of water is (0.40 / 1.20 ) * 100 = 33 1/3%
