Need help with and explanation of reaction and excess problem.

Question

anonymous · Answer

Use the following balanced equation to answer the question:
$$Zn + 2HCl \rightarrow ZnCl _{2} + H _{2}$$

If 35.0 grams of HCl react with excess Zn, how many grams of $$ZnCl _{2}$$ are made?

anonymous · Answer

And another one.

$$4Fe (s) + 3 O _{2} (g) \rightarrow 2Fe _{2}O _{3} (s)$$
If 22.03g of iron is allowed to oxidize with 42.0g of oxygen, what is the mass of $$Fe _{2}O _{3}$$ formed when the reaction is complete?

anonymous · Answer

both they are same... 1 mole of Zn needs 2 mole of Hcl....

so you need to know the number of moles that you have.
 number of mole= wieght/Molecular weight
Molecular weight of HCl=(1)+(35.45)=36.45
   number of mole=35/36.45=0.96

anonymous · Answer

from the equation   2 mole of Hcl gives 1 mole ZnCL2
so 0.96HCL should gives......0.96/2=0.48 mole
now you need to convert number of moles to grams

anonymous · Answer

Moleculart weight of ZnCl2=(65.41)+(35.45)*2=136.31
so the weight is 136.31*.48=65.43 grams