A solution is a solute dissolved in a solvent. The pH scale (0–14, 7 neutral) measures hydrogen ion concentration. Concentration is expressed as % w/w, % v/v, % w/v or molarity, and adding solvent dilutes a solution.
A solution is a solute dissolved in a solvent. It can be gaseous (air), liquid (salt in water) or solid (alloys).
Molar mass: add the atomic masses of all atoms in the formula. For example NaCl = 23 + 35.5 = 58.5 g/mol, and glucose C₆H₁₂O₆ = 180 g/mol.
Concentration units: % w/w is mass of solute per mass of solution × 100; % v/v is volume of solute per volume of solution × 100; % w/v is grams of solute per 100 mL of solution; molarity is moles of solute per dm³ of solution.
Worked idea: to make 1 litre of 0.5 mol/litre NaCl, weigh 0.5 × 58.5 = 29.25 g of salt, dissolve it, and make the volume up to 1 litre.
Dilution: adding solvent lowers the concentration while the amount of solute stays the same, so C₁V₁ = C₂V₂.
pH scale: below 7 is acidic, 7 is neutral and above 7 is basic; each unit is a ten-fold change in hydrogen ion concentration.
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