a stock solution of perchloric acid is 75.5% perchloric acid and has a density of 1.67g/ml. What is the molarity of the solution?
75,5% (w/w??) = 75.5 g HClO4/100 g soln
mols HClO4 = grams/molar mass = ?
Use density to convert 100 g soln to volume (in mL) and convert to L.
Then M = mols/L soln.
To find the molarity of the solution, you need to know the concentration of perchloric acid in moles per liter (M).
First, you need to calculate the number of grams of perchloric acid in one milliliter (ml) of the solution.
Given:
- The stock solution contains 75.5% perchloric acid, which means that 75.5 grams of perchloric acid are present in 100 grams of the solution.
- The density of the solution is 1.67 g/ml.
So, the number of grams of perchloric acid in one ml of solution can be calculated as follows:
Mass of perchloric acid in 1 ml of solution = 75.5% of 1 ml
= (75.5/100) * 1 g
= 0.755 g
Next, you need to convert grams of perchloric acid to moles. The molar mass of perchloric acid (HClO4) is approximately 100.46 g/mol.
Number of moles of perchloric acid in 1 ml of solution = mass of perchloric acid / molar mass
= 0.755 g / 100.46 g/mol
≈ 0.00752 mol
Since the molarity is defined as the number of moles of solute per liter of solution, you need to convert the volume of the solution from ml to L.
The density of the solution is given as 1.67 g/ml. Therefore, the mass of 1 L (1000 ml) of solution can be calculated as:
Mass of 1000 ml of solution = 1.67 g/ml * 1000 ml
= 1670 g
Finally, you can calculate the molarity (M) of the solution using the formula:
Molarity (M) = number of moles / volume of solution in liters
= 0.00752 mol / 1 L
= 0.00752 M
Therefore, the molarity of the perchloric acid solution is approximately 0.00752 M.