97.22 grams of magnesium is needed.
<u>Explanation:</u>
The molar ratio of Mg to O2 to make MgO is 2:1
Here, we have 2 moles of O2, therefore we need 4 moles of Mg.
1 mol of Mg = 24.305 g
Therefore
4 moles of Mg = 4 
24.305 g
= 97.22 g
Hence we need 97.22grams of magnesium are needed to completely reactwith 2.00 mol of O2 in the synthesis reaction that producesmagnesium oxide.
The correct is this because they said
The reactivity of metals increases as you move left in a period and as you move down in a group, so Marie needs to know the period and group of the element inside each box. Boxes that show locations in groups 1 or 2 or in period 8 contain the most reactive elements.
Solution :
Assuming all Al will be consumed in the reaction.
From the given equation, 2 mole of Al produce 2 mole of 
.
So, 1 mole of Al produce 1 mole of . .....statement 1)
Number of moles of Al in 258 gram of Al.
Therefore, from statement 1) number of moles of produced is also 9.556 moles.
