A) 10.0g of Iron is

of Iron.
One mole of dihydrogen is required to form one mole of iron, hence you'll need

of dihydrogen.
B) Likewise : 2.50g of Iron is

of Iron, hence we'll need

of Fe2O3.
Fluorine ions reacts with Hydrogen chloride to form more hydrogen fluoride.
Therefore, moles of HCl = 0.005 l × 0.01 M = 5 ×10^-5 moles
The initial moles of Hydrogen fluoride will be;
= 0.0126 M× 0.0250 = 0.00315 Moles
Moles of hydrogen fluoride after the addition of HCl
= 0.00315 + 5.0× 10^-5 = 0.0032 moles
Therefore, the concentration of Hydrogen chloride
= 0.0032 moles/ 0.030 L
= 0.107 M
Answer:
Two elements because Can is one element and Cl is another. The two is a coeficient that states how many of that element there is.
I hope this helps you!!!