According to the following reaction, how many grams of hydrogen gas will be formed upon the complete reaction of 28.4 grams of hydrobromic acid?

Question

hydrobromic acid (aq) hydrogen (g) + bromine (l) 

Answer 1

2HBr ==> H₂ + Br₂

moles HBr present = 28.4 g x 1 mole/80.9 g = 0.351 moles

moles H₂ produced = 0.351 moles HBr x 1 moles H₂/2 mole HBr = 0.176 moles H₂

mass H₂ = 0.176 moles H₂ x 2 g/mole = 0351 g H₂ gas formed