A perchloric acid solution is composed of 168.75 g of perchloric acid and 81.25 mL of pure water. What is the percent by mass of the perchloric acid solution? The density of
water is 1.000 g/mL.
When I did this part I got 67.5%
But, I am having trouble with the secind part.
The density of the above perchloric acid solution is 1.138 g/mL. What is the molarity of the perchloric acid solution?
I know molarity is moles solute/liter of solution, but how do i find that from %mass? please help if you can!! Thanks!
:) Thanks you so much! :)
To find the molarity of the perchloric acid solution, you'll need to first determine the amount of perchloric acid in moles, and then divide it by the volume of the solution in liters.
Let's start by calculating the moles of perchloric acid. To do this, we need the molar mass of perchloric acid (HClO4). The atomic masses of hydrogen (H), chlorine (Cl), oxygen (O), and four oxygen atoms in perchloric acid are approximately 1.008 g/mol, 35.453 g/mol, 15.999 g/mol, and 15.999 g/mol, respectively.
The molar mass of perchloric acid (HClO4) is:
(1 * 1.008) + (1 * 35.453) + (4 * 15.999) = 100.457 g/mol
Now, we can calculate the moles of perchloric acid in the solution:
moles of perchloric acid = mass of perchloric acid / molar mass of perchloric acid
moles of perchloric acid = 168.75 g / 100.457 g/mol
Next, we need to convert the volume of the solution from milliliters to liters. Since there are 1000 milliliters in a liter, the volume of the solution is:
volume of solution = 81.25 mL / 1000 mL/L
Now, we can find the molarity of the perchloric acid solution by dividing the moles of perchloric acid by the volume of the solution in liters:
molarity = moles of perchloric acid / volume of solution
Plug in the values you obtained and calculate the molarity of the perchloric acid solution.
You have 67.5 g HClO4 in 100 g soln.
Convert 67.5 g HClO4 to moles.
Using the density, convert 100 g soln to mL, then M = moles/L.