how would you prepare 500 ml of .2M solution starting with solid NaH2PO4*H20?
How many moles do you want? That's M x L = 0.2 x 0.500 =?
Then mols = grams/molar mass. You know mols and molar mass, solve for grams.
Weigh out that many grams, place in a 500 mL volumetric flask, swirl until all of the solid is dissolved, make to the mark with distilled water, shake thoroughly.
To prepare a 500 ml solution of 0.2M NaH2PO4·H2O, you will need to know the molar mass of NaH2PO4·H2O and the volume of the solution you want to prepare. Here's how you can calculate the amount of solid NaH2PO4·H2O needed:
1. Determine the molar mass of NaH2PO4·H2O:
- The molar mass of Na (sodium) is approximately 22.99 g/mol.
- The molar mass of H (hydrogen) is approximately 1.01 g/mol.
- The molar mass of P (phosphorus) is approximately 30.97 g/mol.
- The molar mass of O (oxygen) is approximately 16.00 g/mol.
- The molar mass of H2O (water) is approximately 18.02 g/mol.
Using these values, you can calculate the molar mass of NaH2PO4·H2O:
Molar mass = (22.99 * 1) + (1.01 * 2) + 30.97 + (16.00 * 4) + (18.02 * 1) = 156.01 g/mol
2. Calculate the amount of solid NaH2PO4·H2O needed to make the solution:
To prepare a 0.2M solution, you need 0.2 moles of NaH2PO4·H2O per liter (L) of solution.
Number of moles = Molarity * Volume (in L) = 0.2 moles/L * 0.5 L = 0.1 moles
Now, we need to convert moles to grams using the molar mass:
Mass (g) = Number of moles * Molar mass = 0.1 moles * 156.01 g/mol = 15.60 g (rounded to two decimal places)
Therefore, you will need approximately 15.60 grams of solid NaH2PO4·H2O to prepare the 500 ml solution.
3. Dissolve the calculated amount of solid NaH2PO4·H2O in sufficient distilled water to achieve a final volume of 500 ml. Ensure the solid is fully dissolved before finalizing the volume.
Please note that when working with chemicals, it is important to follow safety guidelines and wear appropriate protective equipment.