Final answer:
To obtain 40 grams of magnesium sulfate from a 20% solution, you need 200 milliliters of the solution.
Step-by-step explanation:
To calculate the milliliters of a 20% magnesium sulfate solution needed to obtain 40 grams of magnesium sulfate, you can use the formula for percent concentration: percent concentration = (mass of solute / volume of solution) × 100. In this case, the concentration is 20%, and the mass of magnesium sulfate is 40 grams. To find the volume (V) in milliliters (mL) that contains 40 grams of magnesium sulfate in a 20% solution, you would set up the equation like this:
20% = (40g / V) × 100
To solve for V, rearrange the equation:
20 / 100 = 40g / V
V = 40g / (20 / 100)
V = 40g / 0.2
V = 200 mL
Therefore, 200 milliliters of a 20% magnesium sulfate solution are required to contain 40 grams of magnesium sulfate.