Experiment 9 — Read the pH

Topic: Chemistry · Class 10 · Acids, bases and salts: the pH scale

Aim: Identify the strong acid among the four samples using a pH scale.

Daily: Farmers test soil pH before choosing a crop, doctors treat acidity with antacids, and toothpaste is basic because tooth decay begins when mouth pH falls below about 5.5.

Question: Vinegar and dilute HCl are both acids. Which has the lower pH?

Exp: HCl ionises completely, giving far more H⁺ ions and a much lower pH.

Question: A solution of pH 2 compared with pH 4 is…

Exp: Each unit is a tenfold change.

Question: Tooth decay begins when mouth pH falls below about…

Exp: Enamel starts to corrode.

Question: Acids show acidic behaviour only…

Exp: They must ionise to give H⁺ ions.

Question: An acid plus a base gives…