Sodium chloride is formed through the neutralization reaction between hydrochloric acid (HCl), which is a strong acid, and sodium hydroxide (NaOH), which is a strong base. Because both reactants are strong, the resulting salt is neutral with a pH of approximately 7.

Gastric juice in the human stomach contains a significant concentration of hydrochloric acid (HCl). This acid is secreted by the parietal cells of the stomach lining and serves a critical role in digestion by denaturing proteins and activating the enzyme pepsin, while also providing a defense mechanism against ingested pathogens.

Sulphuric acid (H2SO4) is a strong acid, so its pH is significantly lower than 7, not 7.5. Furthermore, sulphuric acid consists of hydrogen, sulphur, and oxygen; it does not contain phosphorus. Therefore, both provided conclusions are factually incorrect regarding the properties of sulphuric acid.

Phosphoric acid is a common additive in many colas and carbonated soft drinks. It provides a sharp, tangy, or sour flavor profile and also acts as a preservative to inhibit the growth of molds and bacteria in the sugary solution.

Acids only exhibit their characteristic properties, such as changing the color of litmus paper, when they dissociate into ions in the presence of water. Dry HCl gas does not contain free hydrogen ions (H+). Without moisture to facilitate ionization, the litmus paper remains unchanged, demonstrating that water is essential for acidic behavior.

Alkalis are basic substances that turn red litmus paper blue, not blue to red. The statement claiming blue litmus turns red is false because that is a characteristic property of acids. Alkalis generally exhibit a bitter taste, a soapy or slippery feel, and act as electrolytes in aqueous solutions due to the presence of hydroxide ions.

A salt is a chemical compound formed by the neutralization reaction between an acid and a base (alkali). In this process, the hydrogen ions from the acid and the hydroxide ions from the base combine to form water, while the remaining ions form the salt. This is a fundamental principle of acid-base chemistry.

When a carbonate or bicarbonate reacts with a strong acid like HCl, a chemical reaction occurs that produces salt, water, and carbon dioxide gas. The rapid release of CO2 gas causes visible effervescence or bubbling in the reaction mixture.

Acids containing hydrogen, oxygen, and a non-metal are classified as oxyacids (or oxoacids). In contrast, hydracids are binary acids containing only hydrogen and a non-metal (like HCl). The term 'hydra/oxy' in the options refers to this distinction between hydracids and oxyacids, which is a standard classification based on elemental composition.

Statement 1 is correct because metallic oxides are generally basic. Statement 3 is correct because all acids share common properties, such as reacting with bases to form salts. Statement 2 is incorrect because non-metallic oxides are typically acidic, not basic, in nature.