Final answer:
The correct answer would be (not listed in the original options). To calculate the mass of CaSO4, the number of moles was first determined and then multiplied by the molar mass of CaSO4, resulting in a value converted to milligrams. The final mass of CaSO4 added to the flask was calculated to be 32.0 milligrams.
Step-by-step explanation:
The question is how to calculate the mass in milligrams of calcium sulfate (CaSO4) when a chemist adds 270.0 mL of an 8.7×10-4 M CaSO4 solution to a flask. To find the mass of CaSO4, first calculate the number of moles of CaSO4 in solution:
Number of moles of CaSO4 = Volume (L) × Molarity (M)
270.0 mL = 0.270 L (since 1000 mL = 1 L), so:
Number of moles = 0.270 L × 8.7×10-4 M = 0.000235 mol
Next, we calculate the mass of CaSO4 in grams using its molar mass (136.14 g/mol)
Mass (g) = Number of moles × Molar mass (g/mol)
Mass = 0.000235 mol × 136.14 g/mol = 0.0319951 g
Finally, convert the mass to milligrams:
0.0319951 g = 31.9951 mg
When considering significant figures, the answer should be reported as 32.0 mg because the volume was given with four significant figures, and the molarity was given with two significant figures.
The correct answer would be (not listed in the original options):