What is meant by the 'concentration' of a solution? Describe two different ways to express the concentration of a solution, providing the formula for each.

The concentration of a solution refers to the amount of solute present in a given amount of solution or solvent. Two common ways to express concentration are: 

1. Mass by Mass Percentage of a Solution: 
   Formula: (Mass of solute / Mass of solution) × 100 
2. Mass by Volume Percentage of a Solution: 
   Formula: (Mass of solute / Volume of solution) × 100