Which one among the following statements is correct ?

In chemistry, the relationship between bases and alkalis is defined by their solubility in water. A base is a substance that can neutralize an acid, but not all bases are capable of dissolving in water [1]. An alkali is specifically defined as a base that is soluble in water [2]. For example, sodium hydroxide and potassium oxide are alkalis because they dissolve in water to produce hydroxide ions [2]. Conversely, many metal oxides, such as copper oxide or magnesium oxide, are bases because they react with acids to form salt and water, but they are not classified as alkalis because they are insoluble in water [2]. Therefore, while every alkali is inherently a base, not every base qualifies as an alkali, making the statement 'All alkalis are bases but all bases are not alkalis' the only correct choice [1].

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 2: Acids, Bases and Salts > QUESTIONS > p. 24
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 3: Metals and Non-metals > Activity 3.9 > p. 41