Question 2
What is the unit of concentration as chemistry most often expresses it?
The right answer is the one marked above.
mol dm-3. Concentration is the amount of solute in moles divided by the volume of solution in cubic decimetres.
g dm⁻³ is the m/v way of stating a composition and g mol⁻¹ is a molar mass. Chemistry prefers moles because reactions happen between particles, and equal concentrations in mol dm⁻³ mean equal numbers of particles.