Question

How many grams of potassium dichromate (K₂ Cr₂O7) are required to prepare 250 mL solution that is

2.16 M?
O 12g
2541.9
0.002 g
O 159g

Answer 1

To prepare a 250 mL 2.16 M solution of potassium dichromate, 159 grams of the compound are required.

Step-by-step explanation:

To determine the number of grams of potassium dichromate (K2Cr2O7) needed to prepare a 250 mL solution with a concentration of 2.16 M, we use the equation:

moles = concentration (M) × volume (L)

First, we convert the volume from mL to L:

250 mL = 250/1000 L = 0.25 L

Next, we rearrange the equation to solve for moles:

moles = 2.16 M × 0.25 L = 0.54 moles

Finally, we use the molar mass of potassium dichromate (K2Cr2O7) to convert moles to grams:

grams = moles × molar mass

The molar mass of K2Cr2O7 can be calculated as:

(2 × molar mass of K) + (2 × molar mass of Cr) + (7 × molar mass of O)

Using the atomic masses from the periodic table, we find:

(2 × 39.10 g/mol) + (2 × 52.00 g/mol) + (7 × 16.00 g/mol) = 294.18 g/mol

Therefore, the number of grams of potassium dichromate needed is:

grams = 0.54 moles × 294.18 g/mol = 159 g

Learn more about Calculating grams of a compound needed for a specific concentration