Answer
A) $\rho=2.331\ g/mL$
B) 11.73 mL of $CHCl_3$ and 8.27 mL of $CHBr_3$
Work Step by Step
Density definition: $\rho=\frac{m}{V}$
A) Calculating the masses from the given data:
$CHCl_3$ ($\rho=1.492\ g/mL,\ V=10.0\ mL$):$m=14.92\ g$
$CHBr_3$ ($\rho=2.890\ g/mL,\ V=15.0\ mL$): $m=43.35\ g$
Calculating the density of the mixture $m=58.27\ g,\ V=25.0\ mL$:
$\rho=2.331\ g/mL$
B) Total volume: 20mL
Defining a variable for one's volume and calculating the volume of the other as a function of that variable:
$CHCl_3$ volume: V
$CHBr_3$ volume: 20-V
Calculating the total mass of the mixture from the given data:
($\rho=2.07\ g/mL,\ V=20.0\ mL$):
$m=41.4\ g$
Applying that the mass of the mixture must be equal to the sum of the individual masses of its components:
$41.4=1.492\times V + 2.890\times (20-V)$
And Silvinha for V:
$V=11.73\ mL$
