The density of a solution of 3.69g KBr in 21.70g H2O is 1.11g/mL. What is the %w/v of KBr in the solution?
What volume is 21.70g?
volume = mass/density
Then (3.69/mL volume) x 100
Mass of solution
= 3.69g + 21.70g
=25.39 g
Volume of solution
= 25.39g / 1.11g/mL
=22.9 mL
= 0.0229 L
Moles KCl
= 3.69 g / 74.5513g/mol
= 0.0494961 mol
Molarity of KCl
= 0.0494961 mol / 0.0229L
= 2.1614 mol/L
Now just do that for KBr instead of KCl i.e change the molecular weight in step 3
To find the percent weight/volume (%w/v) of KBr in the solution, we need to determine the weight of KBr dissolved in a given volume of solution.
First, let's calculate the volume of the solution. We have the density of the solution, which is given as 1.11g/mL. Density is defined as mass divided by volume (D = m/v). Rearranging the equation to solve for volume, we have:
Volume (v) = mass (m) / density (D)
In this case, the mass of the solution is the sum of the masses of KBr and H2O, which is given as 3.69g KBr + 21.70g H2O. Therefore:
v = (3.69g KBr + 21.70g H2O) / (1.11g/mL)
Next, we need to calculate the mass of KBr in the solution. We are given that the solution contains 3.69g KBr.
To find the %w/v, we divide the mass of KBr by the volume of the solution and multiply by 100:
%w/v = (mass of KBr / volume of solution) * 100
Plugging in the values, we have:
%w/v = (3.69g KBr / v mL) * 100