how many grams of potassium dichromate are needed to make 250 mL of a 0.75 molar solution?
See your other post above.
To determine the number of grams of potassium dichromate needed to make a 0.75 molar solution in 250 mL, we need to follow a few steps:
Step 1: Determine the molar mass of potassium dichromate (K2Cr2O7).
To calculate the molar mass, find the atomic masses of all the elements in the compound and multiply them by their respective subscripts:
- Atomic mass of K (potassium) = 39.10 g/mol
- Atomic mass of Cr (chromium) = 52.00 g/mol
- Atomic mass of O (oxygen) = 16.00 g/mol
Thus, the molar mass of K2Cr2O7 = (2*39.10) + (2*52.00) + (7*16.00) = 294.18 g/mol
Step 2: Convert molarity to moles.
Molarity (M) is defined as the number of moles of solute per liter of solution. Since the volume provided is 250 mL (0.250 L), we can use the formula:
Moles (mol) = Molarity (M) * Volume (L)
Moles = 0.75 mol/L * 0.250 L = 0.1875 mol
Step 3: Convert moles to grams.
To convert moles to grams, multiply the number of moles by the molar mass of the compound:
Grams = Moles * Molar mass
Grams = 0.1875 mol * 294.18 g/mol ≈ 55.14 g
Therefore, approximately 55.14 grams of potassium dichromate are needed to make 250 mL of a 0.75 molar solution.