Test: pH Scale & Its Importance - Class 9 MCQ

Yellowish orange colour on pH paper is shown by acidic substances hence to change the colour of pH paper to greenish blue (pH = 8), an antacid should be added since antacids are basic in nature.

Less than 6.0 
pH range ( 5-6) shows up yellow colour on pH paper. 

Strong bases have very high pH values, usually in range 12 to 14.

1.Sodium bicarbonate (as it is a base and has pH value more than 7) .
2. Water (as it is neutral and has pH value as 7) .
3. Lemon juice (it is acidic and the pH value is less than 7).

Formic acid is also present in a natural state in stinging nettles, and is reponsible for the burning feeling on contact with them. It is also found in the stings and bites of many insects, including bees and ants, which use it as a chemical defence mechanism.

Pure distilled water should be neutral with a pH of 7, but because it absorbs carbon dioxide from the atmosphere, it's actually slightly acidic with a pH of 5.8.

Due to eating more sweets and sugary things the particles of sugar will remain left in our mouth the bacteria present in our mouth causes the degradation of these sugar particles to produce large amount of acid which result in decrease of pH of mouth from 5.5 ultimately it lead to tooth decay.Tooth decay starts when pH is lower than 5.5 this is because the acid attack the enamel of our teeth and corrode it.

Both acetic acid and ethanoic acid can turn the pH paper orange. Sodium carbonate is basic in nature.

HCl is a strong acid and has pH = 1 and hence turns the pH paper red.

A solution that is neither acidic nor basic is neutral and has a pH of 7.