A sample of 'soft soap' contains

Soaps are chemically defined as the sodium or potassium salts of long-chain carboxylic acids (fatty acids) [1][2]. The physical consistency of the soap depends on the alkali metal used during the saponification process. Sodium salts of fatty acids generally produce 'hard soap', which is commonly used for solid bars [3]. In contrast, potassium salts of fatty acids produce 'soft soap' or liquid soap. These potassium-based soaps are often milder, more soluble in water, and are used in products like liquid hand soaps, shaving creams, and baby soaps. Calcium and magnesium are typically associated with water hardness and form insoluble precipitates (scum) when they react with soap, rather than being the primary constituent of the soap itself [3]. Therefore, a sample of 'soft soap' contains potassium [2].

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 4: Carbon and its Compounds > Activity 4.10 > p. 75
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 4: Carbon and its Compounds > CH COOH CH CH OH CH C C CH CH H O 3 3 2 3 2 3 2 Acid O (E - + - - - - - + thanoic acid) (Ethanol) (Ester) O > p. 73
3. [3] Science , class X (NCERT 2025 ed.) > Chapter 4: Carbon and its Compounds > Activity 4.12 > p. 76