Question

Hydrobromic acid dissolves solid iron according to the

following reaction:
Fe(s) + 2 HBr(aq) → FeBr2(aq) + H2(9)

Part A
What mass of HBr (in g) would you need to dissolve a 3.2 - g pure iron
Express your answer using two significant figures.

Part B
What mass of H, would be produced by the complete reaction of the iron

Answer 1

A. 9.3 g

B. 0.11 g

Step-by-step explanation:

• Fe(s) + 2HBr(aq) → FeBr₂(aq) + H₂(g)

PART A

First we convert 3.2 grams of pure iron into moles, using its molar mass:

• 3.2 g ÷ 55.85 g/mol = 0.0573 mol Fe

Now we convert 0.0573 moles of Fe into moles of HBr, using the stoichiometric coefficients:

• 0.0573 mol Fe *
  `(2molHBr)/(1molFe)` = 0.115 mol HBr

Finally we convert 0.115 moles of HBr into grams, using its molar mass:

• 0.115 mol HBr * 80.91 g/mol = 9.3 g HBr

PART B

This time we convert the 0.0573 moles of Fe from last time into H₂ moles:

• 0.0573 mol Fe *
  `(1molH_2)/(1molFe)` = 0.0573 mol H₂

Finally we convert H₂ moles into grams:

• 0.0573 mol H₂ * 2 g/mol = 0.11 g