Respuesta :
Answer: The amount of HBr required to dissolve a given amount of pure iron bar is 7.76 grams.
Explanation:
To calculate the number of moles, we use the equation:
[tex]\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}[/tex] .....(1)
Given mass of iron = 2.7 g
Molar mass of iron = 55.84 g/mol
Putting values in equation 1, we get:
[tex]\text{Moles of iron}=\frac{2.7g}{55.84g/mol}=0.048mol[/tex]
The chemical equation for the reaction of HBr and pure iron follows:
[tex]Fe(s)+2HBr(aq.)\rightarrow FeBr_2(aq.)+H_2(g)[/tex]
By Stoichiometry of the reaction:
1 mole of iron metal reacts with 2 moles of HBr
So, 0.048 moles of iron metal will react with = [tex]\frac{2}{1}\times 0.048=0.096mol[/tex] of HBr
Now, calculating the mass of HBr by using equation 1, we get:
Molar mass of HBr = 80.91 g/mol
Moles of HBr = 0.096 moles
Putting values in equation 1, we get:
[tex]0.096mol=\frac{\text{Mass of HBr}}{80.91g/mol}\\\\\text{Mass of HBr}=(0.096mol\times 80.91g/mol)=7.76g[/tex]
Hence, the amount of HBr required to dissolve a given amount of pure iron bar is 7.76 grams.
The mass of HBr that would be needed to dissolve the 2.7 g pure iron bar is 7.8 g
To determine the mass of HBr that would be needed to dissolve the 2.7 g pure iron bar,
First, we will write a balanced chemical equation for the reaction
The balanced chemical equation for the reaction is
Fe(s) + 2HBr(aq) → FeBr₂(aq) + H₂(g)
This means,
1 mole of Fe is required to completely react with 2 moles of HBr
Now, we will determine the number of moles of Fe present in the 2.7g iron bar
Using the formula
[tex]Number \ of\ moles = \frac{Mass}{Atomic\ mass}[/tex]
Atomic mass of Fe = 55.845 g/mol
∴ Number of moles of Fe present = [tex]\frac{2.7}{55.845 }[/tex]
Number of moles of Fe present = 0.048348 mol
Since,
1 mole of Fe is required to completely react with 2 moles of HBr
Then,
0.048348 mole of Fe will completely react with 2 × 0.048348 mole of HBr
2 × 0.048348 = 0.096696 mole
∴ The number of moles of HBr required is 0.096696 mole
Now, for the mass of HBr that would be needed
From the formula
Mass = Number of moles × Molar mass
Molar mass of HBr = 80.91 g/mol
∴ Mass of HBr required = 0.096696 × 80.91
Mass of HBr required = 7.82367 g
Mass of HBr required ≅ 7.8 g
Hence, the mass of HBr that would be needed to dissolve the 2.7 g pure iron bar is 7.8 g
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