How Many Protons [Or, More Accurately, Hydronium Ions (H₃O⁺)] Are

Multiple Choice

How many protons [or, more accurately, hydronium ions (H₃O⁺) ] are there in a spherical lysosome that is about 0.6 µm in diameter and maintains an interior pH of about 5.0? Recall that the volume of a sphere of radius r is calculated as V = 4/3 × π × r³, and that pH = -log [H⁺]. Avogadro's constant is approximately 6 × 10²³ molecules/mole.

A) About 700 ions
B) About 7000 ions
C) About 70,000 ions
D) About 700,000 ions
E) About 7,000,000 ions