A compound<span> is a </span>molecule<span> that contains at least two different elements. </span>All compounds<span> are </span>molecules<span> but not </span>all molecules<span> are </span>compounds<span>. </span>Molecularhydrogen (H2<span>), </span>molecular<span> oxygen (O</span>2<span>) and </span>molecular<span> nitrogen (N</span>2) are notcompounds<span> because each is composed of a single element.</span>
<u>Answer:</u> The limiting reagent in the reaction is bromine.
<u>Explanation:</u>
Limiting reagent is defined as the reagent which is completely consumed in the reaction and limits the formation of the product.
Excess reagent is defined as the reagent which is left behind after the completion of the reaction.
Given values:
Moles of iron = 10.0 moles
Moles of bromine = 12.0 moles
The chemical equation for the reaction of iron and bromine follows:

By the stoichiometry of the reaction:
If 3 moles of bromine reacts with 2 moles of iron
So, 12.0 moles of bromine will react with =
of iron
As the given amount of iron is more than the required amount. Thus, it is present in excess and is considered as an excess reagent.
Hence, bromine is considered a limiting reagent because it limits the formation of the product.
Thus, the limiting reagent in the reaction is bromine.
The coefficient for hydrogen in the balanced equation of solid molybdenum(iV) oxide with gaseous hydrogen is 2
Explanation
Coefficient is defined to as a number in front of a chemical formula in a balanced chemical equation.
The reaction of molybdenum (iv) oxide with gaseous hydrogen is as below,
MoO2 + 2 H2→ Mo +2 H2O
From balanced equation above the coefficient for H2 is 2 since the number in front of H2 is 2