Test: Properties of Acids & Bases - UPSC MCQ

Turmeric solution or paper turns reddish brown with base. Turmeric does not change color with acid.

Blue litmus paper turns red under acidic conditions and red litmus paper turns blue under basic or alkaline conditions

Distilled water do not conduct electricity. The reason is that a liquid conducts electricity is by the positively or negatively charged ions that are actually moving from one of the electrodes to the other, carrying charge (electricity) with them.

Since Sodium hydroxide is a base and thus it has no effect on a blue litmus paper but it changes red litmus to blue.

- Acids and Bases: Blue litmus turns red in the presence of an acid.
- Identifying the Acid:
- Mg(OH)₂: Magnesium hydroxide is a base.
- NaOH: Sodium hydroxide is a strong base.
- NH₄OH: Ammonium hydroxide is a weak base.
- CH₃COOH: Acetic acid is a weak acid.
- Correct Answer: Acetic acid (CH₃COOH) can turn blue litmus red because it is an acid.

Phenolphthalein is often used as an indicator in acid–base titrations. For this application, it turns colourless in acidic solutions and magenta in basic solutions.

All acids contain hydrogen, but not all hydrogen-containing compounds are acids. Most acids also contain oxygen.

Methyl orange is a pH indicator frequently used in titration because of its clear and distinct colour variance at different pH values. Methyl orange shows pink colour in acidic medium and yellow colour in basic medium. Because it changes colour at the pH of a mid strength acid, it is usually used in titration for acids. Unlike a universal indicator, methyl orange does not have a full spectrum of colour change, but it has a sharp end point.

An olfactory indicator is a material whose smell varies reliant on whether it is mixed with an acidic or basic solution. Olfactory indicators mainly used in laboratory to test whether a solution is a base or an acid. Onion is an example of olfactory indicators. 

As metal carbonates react with acid, a neutralisation reaction happens. Salt, water, and carbon dioxide are produced. This can be expressed in the following general equation:

metal carbonate + acid → salt + water + carbon dioxide

Reaction of a strong acid with strong base is called neutralization reaction which produces salt and water,

HCl + NaOH → NaCl + H₂O

This equation is already balanced.

The property of carbon dioxide to behave like an acid and react with an alkali makes it an acidic oxide. Acidic oxides are a type of oxides that react with alkalis to form salt and water.

Marble chips are the substances that have the formula CaCO₃
Calcium carbonate reacts with sulphuric acid to form calcium sulphate and carbon dioxide which turns lime water milky.

CaCO₃ + H₂SO₄ → CaSO₄ + CO₂ + H₂O

When copper oxide and dilute hydrochloric acid are mixed the blue green solution is formed. 
The reaction is :- 
CuO + 2HCl → CuCl2 + H2O

Bleaching powder is produced by the action of chlorine on slaked lime.