How many grams of HCl are formed from reaction of 3.58g of H2 with 8.90g of Cl2?

Answer 1

H2 + Cl2 ==> 2HCl
This is a limiting reagent (LR) problem. You know that because amounts are given for BOTH reactants.
mols H2 = grams/molar mass = ?
mols Cl2 = grams/molar mass = ?

Using the coefficients in the balanced equation, convert mols H2 to mols HCl.
Do the same for mols Cl2 to mols HCl.
It is likely that the two numbers will not be the same which means one is not right; the correct value in LR problems is ALWAYS the smaller value and the reagent responsible for producing that value is the LR.
Now using the smaller value convert that to grams.
g = mols HCl x molar mass HCl.