Respuesta :
Answer:
3.3 %
Explanation:
According to the question , the following reaction takes place -
Ba(OH)₂ + 2 HBr → BaBr₂ + 2 H₂O
Molarity of a substance , is the number of moles present in a liter of solution .
M = n / V
M = molarity
V = volume of solution in liter ,
n = moles of solute ,
According to the question ,
V = volume of Ba(OH)₂ = 19.5 mL = 0.0195 L ( since , 1 ml = 10 ⁻³ L )
M = Molarity of Ba(OH)₂ = 0.374 M
The moles of Ba(OH)₂ can be calculated by using the above equation ,
M = n / V
n = M * V = 0.374 M * 0.0195 L = 0.0072 mol
From the above balanced reaction ,
2 mol of HBr reacts with 1 mol Ba(OH)₂
1 mol of HBr reacts with 1 / 2 mol Ba(OH)₂
From the above data ,
1 mol HBr reacts with = 1 / 2 * 0.0072 mol = 0.0036 mol
Hence , number of moles of HBr = 0.0036 mol
Now,
Moles is denoted by given mass divided by the molecular mass ,
Hence ,
n = w / m
n = moles ,
w = given mass ,
m = molecular mass .
As calculated above ,
n = 0.0036 mol
As we know , the m = molecular mass of HBr = 81 g/mol
n = w / m
w = n * m = 0.0036 mol * 81 g/mol = 0.2916 g
Now ,
mass % = mass of HBr / mass of solution * 100
mass % = 0.2916 g / 8.72 g * 100 = 3.3 %
