Question

Consider the substances below.

• 1 mol of beryllium
• 1 mol of salt
• 1 mol of water
• 1 mol of hydrogen

Which statement is true about these substances?
They have exactly the same mass.
They have different numbers of particles.
They have the same number of atoms.
They have different masses.

Answer 1

They have different masses.

Explanation: 1 mole of each substance contains the same number of particles (Avogadro's number, 6.022×10^23), but their molar masses differ (Be ≈ 9.01 g, NaCl ≈ 58.44 g, H2O ≈ 18.02 g, H2 ≈ 2.02 g), so the masses are different.