Acidity and indicators - Free MCQ Practice Test with solutions, Class 7

Citric acid is an acid found in citrus fruits like lemons. Sodium hydroxide and potassium hydroxide are alkalis, and soap is typically made with alkalis.

Tea is an example of a weak acid, with a pH close to neutral (around 5-6). Hydrochloric acid and sulfuric acid are strong acids (pH 0-2), and citric acid is a weak acid (pH around 3-4) but stronger than tea.

A universal indicator turns purple when it comes into contact with a strong alkali, indicating a high pH value (towards 14 on the pH scale).

A universal indicator turns green when it comes into contact with a solution that has a pH of 7, indicating a neutral substance. Alkalis have a pH range of 8-14, which would turn the indicator blue or purple.

When handling strong acids and alkalis, it is important to use protective equipment such as safety goggles, lab coats, and gloves to prevent injury from corrosive or irritant substances.

Acids typically start with hydrogen in their chemical formulas, such as HCl for hydrochloric acid and H₂SO₄ for sulfuric acid. Alkalis often end with hydroxide, and the presence of carbon is more indicative of organic compounds.

A pH of 1 indicates a strong acid, as strong acids have a pH range of 0-2, according to the pH scale.

A pH of 14 indicates a strong alkali, as strong alkalis have a pH range of 12-14, according to the pH scale.

Hydrochloric acid is found in the stomach, as mentioned in the content regarding acids.

Vinegar, being a weak acid with a pH around 2-3, would turn a universal indicator yellow. Soap and potassium hydroxide are alkalis, and bleach is a strong alkali, all of which would turn the indicator blue or purple.