The question asks about the composition of aqua regia, a highly corrosive mixture known for its ability to dissolve noble metals like gold and platinum. We need to identify the correct acids and their volumetric ratio.
The chemical reactions involved in dissolving gold are:
D) Concentrated HNO₃ and concentrated HCl in the ratio 1:3 (by volume) is the correct composition of aqua regia. Concentrated nitric acid acts as an oxidizing agent, and concentrated hydrochloric acid provides chloride ions that stabilize the gold ions by forming tetrachloroaurate(III) complex ions, thus enabling the dissolution of gold.
This question asks for the correct chemical reaction between hydrochloric acid (HCl) and sodium hydroxide (NaOH). This is a classic example of an acid-base neutralization reaction. We need to identify the products formed and ensure the equation is balanced and chemically accurate.
B) HCl + NaOH → NaCl + H₂O (neutralisation reaction)
This option correctly identifies sodium chloride (NaCl) and water (H\(_2\)O) as the products of the reaction between HCl and NaOH, and it correctly labels it as a neutralization reaction. The equation is also balanced.
The question asks for the specific term used to describe bases that are soluble in water. This requires knowledge of the classification of bases based on their solubility.
Correct Option: B) Alkalis are bases that are soluble in water. They produce hydroxide ions (\(\text{OH}^-\)) in aqueous solutions.
This question tests knowledge of the reaction between an amphoteric metal (zinc) and a strong base (sodium hydroxide). Amphoteric metals react with strong bases to form a salt and hydrogen gas.
D) Sodium zincate (\(\text{Na}_2\text{ZnO}_2\)) and hydrogen gas: \(2\text{NaOH} + \text{Zn} \rightarrow \text{Na}_2\text{ZnO}_2 + \text{H}_2\uparrow\). This option correctly identifies both products and provides the balanced chemical equation for the reaction between sodium hydroxide and zinc metal.
This question tests knowledge of basic chemical reactions, specifically the reaction between an acid gas (carbon dioxide) and a strong base (sodium hydroxide). Carbon dioxide is an acidic oxide, and it reacts with bases to form salts and water.
This reaction is commonly used to remove CO₂ from gas streams or to prepare sodium carbonate.
Correct Option: C) Sodium carbonate (Na₂CO₃) is formed: \(2\text{NaOH} + \text{CO}_2 \rightarrow \text{Na}_2\text{CO}_3 + \text{H}_2\text{O}\)
The question asks about the caustic nature of bases, specifically their ability to corrode skin. This involves understanding the chemical reactions that occur when a strong base comes into contact with organic tissue.
D) OH⁻ ions, which react with and denature proteins and saponify fats in skin tissue. This option accurately describes the chemical mechanisms by which hydroxide ions cause damage to skin, making bases caustic.