Final answer:
None of the options provided (a, b, c, d) are correct. The correct mass of potassium chromate needed to make a 1.13M solution in a 250.0 ml volumetric flask is 54.84 grams, which is not listed in the options.
Step-by-step explanation:
To calculate the amount of potassium chromate (K2CrO4) needed to create a 1.13M solution in a 250.0 ml volumetric flask, we must first calculate the number of moles of potassium chromate required for 250.0 ml of solution:
The formula for molarity (M) is:
M = moles of solute / liters of solution
Rearranging the formula to solve for moles gives:
moles of solute = M × liters of solution
Using the 1.13M concentration:
moles of potassium chromate = 1.13 moles/L × 0.250 L
moles of potassium chromate = 0.2825 moles
Next, we need the molar mass of potassium chromate, which can be calculated using the periodic table:
K = 39.10 g/mol (for each of the 2 K ions)
Cr = 52.00 g/mol
O = 16.00 g/mol (for each of the 4 O atoms)
Molar mass of K2CrO4 = 2(39.10 g/mol) + 52.00 g/mol + 4(16.00 g/mol)
Molar mass of K2CrO4 = 194.20 g/mol
Now we can calculate the mass:
mass = moles × molar mass
mass = 0.2825 moles × 194.20 g/mol
mass = 54.84 g
Therefore, the correct answer is not given in the options a), b), c), or d). The student should weigh out 54.84 grams of potassium chromate to create the desired 1.13M solution in a 250 ml flask.