A 7.52 g sample of an aqueous solution of hydrobromic acid contains an unknown amount of the acid.
If 13.5 mL of 0.633 M barium hydroxide are required to neutralize the hydrobromic acid, what is the percent by mass of hydrobromic acid in the mixture?
To find the percent by mass of hydrobromic acid in the mixture, we need to determine the mass of hydrobromic acid and the total mass of the mixture.
First, let's calculate the number of moles of barium hydroxide used in the neutralization reaction:
moles of barium hydroxide = concentration × volume
= 0.633 mol/L × 0.0135 L
≈ 0.00855 mol
According to the balanced chemical equation for the neutralization reaction between hydrobromic acid (HBr) and barium hydroxide (Ba(OH)2), the molar ratio is 2:2. It means that each mole of hydrobromic acid reacts with one mole of barium hydroxide.
Since 0.00855 moles of barium hydroxide were used, the number of moles of hydrobromic acid present in the mixture is also 0.00855 mol.
Now, let's determine the mass of hydrobromic acid:
mass of hydrobromic acid = number of moles × molar mass
= 0.00855 mol × 80.91 g/mol (molar mass of HBr)
≈ 0.692 g
Finally, to find the percent by mass of hydrobromic acid, we divide the mass of hydrobromic acid by the mass of the mixture and multiply by 100:
percent by mass = (mass of hydrobromic acid / mass of mixture) × 100
= (0.692 g / 7.52 g) × 100
≈ 9.2%
Therefore, the percent by mass of hydrobromic acid in the mixture is approximately 9.2%.