Calcium content from CaCO3 composition in eggshell

Steps:

• Mass of eggshell = 10% × 60 g = 6 g
• CaCO3 molar mass = 100 g/mol (Ca = 40 g/mol, C = 12 g/mol, 3O = 48 g/mol)
• Calcium mass fraction in CaCO3 = 40/100 = 0.40
• Mass of calcium = 0.40 × 6 g = 2.4 g ≈ 2 g

Why C is correct:

• Calcium comprises 40% by mass of CaCO3 (atomic mass ratio 40:100), yielding 2.4 g in 6 g shell, which approximates to 2 g given typical eggshell purity.

Why the others are wrong:

• A. 0.2g: Too low; confuses calcium fraction with smaller percentage like 1/30 of shell.
• B. 0.4g: Underestimates shell mass; applies 40% to 1 g instead of 6 g.
• D. 4g: Overestimates; might apply 40% to incorrect 10 g shell mass.

Final answer: C