Answer to Question #95777 in General Chemistry for Brittany Wallace

Question

1. According to the following reaction, how many grams of iron(III) oxide are required for the complete reaction of 28.0 grams of hydrochloric acid?

hydrochloric acid (aq) + iron(III) oxide (s) water (l) + iron(III) chloride (aq)


2. According to the following reaction, how many grams of hydrobromic acid are needed to form 23.4 grams of bromine?

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

Answer 1

1) First we should equalize the equation:

6HCl + Fe₂O₃ = 2FeCl₃ + 3H₂O

Now, we should found the amount in moles of HCl and that of Fe₂O₃ would be 6 times less:

$n(HCl)=\frac{28.0g}{36.5g/mol}=0.767mol$

$n(Fe_2O_3)=\frac{1}{6}*0.767mol=0.128mol$

Thus, the mass of Fe₂O₃ is equal to:

$m(Fe_2O_3)=160g/mol*0.128mol=20.5g$

2) Lets equalize it:

2HBr = H₂ + Br₂

Now, lets calculate the amount of bromine in moles and the amount of HBr would be 2 times Br₂ amount:

$n(Br_2)=\frac{23.4g}{160g/mol}=0.146mol$

$n(HBr)=2*0.146mol=0.292mol$

Now, it is the right time to calculate the mass of HBr:

$m(HBr)=81g/mol*0.292mol=23.7g$

Thus, the mass of HBr required is equal to 23.7g.