Organic acids are chemical compounds containing carbon that exhibit acidic properties. Acetic acid (CH3COOH) is a classic example of a carboxylic acid, which is a major class of organic acids. In contrast, hydrochloric, nitric, and sulphuric acids are inorganic or mineral acids, as they do not contain carbon-hydrogen bonds typical of organic molecules.
3922
Which of the following characteristics is not associated with acidic substances?
Acids are characterized by a sour taste, not a bitter one. Bitter taste is a property typically associated with basic or alkaline substances. The other options correctly describe the chemical behavior of acids in aqueous solutions.
3923
What is the observed effect on dry blue litmus paper when it is exposed to dry hydrogen chloride (HCl) gas?
Acids only exhibit their characteristic properties, such as changing litmus color, in the presence of water where they can dissociate into ions. Dry HCl gas does not contain hydronium ions, so it cannot change the color of dry litmus paper.
3924
Which of the following substances is chemically distinct from the others in terms of its classification as an acid?
While HCl and H2SO4 are strong mineral acids, CH3COOH (acetic acid) is a weak organic acid. However, the question implies a distinction. H2SO4 is a diprotic mineral acid, whereas HCl is monoprotic. Given the options, H2SO4 is often distinguished by its dehydrating properties and polyprotic nature compared to the others.
3925
Match the following acids with their primary natural sources: a) Lactic acid, b) Tartaric acid, c) Oxalic acid, d) Citric acid.
Lactic acid is found in sour curd (a-4). Tartaric acid is found in tamarind (b-1). Oxalic acid is found in tomatoes (c-3). Citric acid is found in oranges (d-2). Matching these pairs correctly leads to option D.
3926
Which of the following statements is scientifically incorrect?
The alkaline nature of sodium hydroxide (NaOH) is due to the presence of hydroxide ions (OH-), not sodium ions (Na+). Sodium ions are spectator ions in this context. Phenolphthalein is a pH indicator that turns pink in basic solutions, and non-metallic oxides like CO2 are acidic.
3927
What are the primary products formed when an acid reacts with a metal oxide?
Metal oxides are basic in nature. When they react with an acid, a neutralization reaction occurs. The reaction between a base (metal oxide) and an acid produces a salt and water as the final products, following the general equation: Metal Oxide + Acid -> Salt + Water.
3928
Which gas is evolved when hydrochloric acid reacts with sodium bicarbonate?
The reaction between sodium bicarbonate (NaHCO3) and hydrochloric acid (HCl) produces sodium chloride, water, and carbon dioxide gas. The chemical equation is NaHCO3 + HCl -> NaCl + H2O + CO2. The rapid release of carbon dioxide gas is responsible for the characteristic effervescence observed during this acid-base reaction.
3929
Which of the following is not a characteristic property of an alkali?
Alkalis are bases that dissolve in water to produce hydroxide ions (OH-), not hydrogen ions (H+). The production of hydrogen ions is a defining characteristic of acids. Alkalis are known for turning red litmus blue, having a slippery or soapy texture, and being capable of breaking down organic matter like fats and proteins.
3930
Evaluate the following statements regarding alkalis: 1. An alkali that is completely ionized in water produces a large number of OH- ions. 2. An alkali that is partially ionized in water produces a large number of OH+ ions.
Statement 1 is correct because strong alkalis like NaOH dissociate completely to release hydroxide ions. Statement 2 is incorrect because alkalis produce hydroxide (OH-) ions, not OH+ ions, and partial ionization refers to weak bases, which produce fewer ions, not a large number.
