Expain the preparation of 250ml of 2.5% v/v H3PO4 (MW=98.0,density=1.71,%purity=85%
To prepare 250 mL of a 2.5% v/v (volume/volume) solution of H3PO4, we need to follow these steps:
Step 1: Calculate the required volume of the concentrated H3PO4 solution.
To do this, we need to know the concentration of the concentrated H3PO4 solution. The % purity provided is 85%.
Concentration of H3PO4 = 85%
This means that 85 mL of the concentrated H3PO4 solution contains 100 mL of pure H3PO4.
Let's calculate the required volume of concentrated H3PO4:
Volume of concentrated H3PO4 = (desired concentration / concentration of H3PO4) * volume of solution
Volume of concentrated H3PO4 = (2.5 / 85) * 250 mL
Step 2: Calculate the required mass of the concentrated H3PO4 solution.
To do this, we need to know the molecular weight (MW) of H3PO4, which is 98.0 g/mol.
Mass of H3PO4 = (volume of concentrated H3PO4 / 100) * (MW * density)
Mass of H3PO4 = (volume of concentrated H3PO4 / 100) * (98.0 g/mol * 1.71 g/mL)
Step 3: Calculate the required volume of water to dilute the concentrated H3PO4 solution.
Volume of water = final volume - volume of concentrated H3PO4
Volume of water = 250 mL - volume of concentrated H3PO4
Once you have obtained the volume of concentrated H3PO4 and the volume of water, you can proceed with the preparation of the solution.
Step 4: Preparation of the solution.
1. Measure the calculated volume of concentrated H3PO4 using a graduated cylinder and transfer it to a clean and dry 250 mL volumetric flask.
2. Add the calculated volume of water to the flask.
3. Mix gently to ensure proper mixing of the components.
4. Once the solution is homogeneous, the preparation of 250 mL 2.5% v/v H3PO4 solution is complete.
Remember to handle concentrated H3PO4 with care as it is corrosive and can cause severe burns. It is also important to wear appropriate personal protective equipment, such as gloves and safety glasses, during the preparation process.