Chemistry

Joseph Black is credited with the discovery of carbon dioxide, which he called 'fixed air,' in the 1750s through his experiments on magnesium carbonate and calcium carbonate.

All acids contain hydrogen atoms that can be released as hydrogen ions (H+) in aqueous solutions, which is the defining characteristic of acids. Therefore, hydrogen is the element common to all acids.

Crude oil is typically heated in a furnace to around 400°C before entering the distillation column for fractional distillation. This temperature is sufficient to vaporize most components without cracking the hydrocarbons.

Carbon, diamond, and graphite are different structural forms of the same element carbon, known as allotropes. Allotropes have different physical properties but the same chemical element.

Ammonia is a compound consisting of one nitrogen atom and three hydrogen atoms, giving it the molecular formula NH3. This is the standard and widely accepted formula for ammonia.

The ozone (O3) molecule consists of covalent bonds between oxygen atoms. While resonance structures can be drawn showing partial double bonds, the bonding is fundamentally covalent, not dative or ionic. Therefore, the correct answer is 'Covalent bond.'

Lithium is the most reducing agent among the given options because it has a strong tendency to lose electrons and form positive ions, making it highly reactive and a strong reducing agent. Chlorine is an oxidizing agent, while helium and neon are inert noble gases and do not act as reducing agents.

The temperature at which two conjugate (miscible) solutions become completely miscible in all proportions, forming one homogeneous phase, is called the consolute temperature. This is a well-known term in solution chemistry, distinguishing it from azeotrope, eutectic point, and the incorrect term 'conjugate temperature.'

Nitric acid is a well-known chemical compound with the molecular formula HNO3, which consists of one hydrogen atom, one nitrogen atom, and three oxygen atoms. This formula correctly represents nitric acid, making option B the correct answer.

An emulsion is a colloidal system where a liquid is dispersed in another liquid, such as oil in water or water in oil. This matches the definition given in the question, making 'Emulsion' the correct answer.