The question asks to identify the acid responsible for the sour taste of vinegar. This requires knowledge of common acids and their natural sources or primary applications.
Correct Option: C) Acetic acid (CH₃COOH — ethanoic acid) is the primary component of vinegar and is responsible for its sour taste. Its chemical formula is \( \text{CH}_3\text{COOH} \) and it is also known as ethanoic acid.
This question tests fundamental knowledge of chemical reactions, specifically the reaction between metals and dilute acids. Understanding the general reactivity series of metals and the products formed in such reactions is key.
\[ \text{Metal} + \text{Dilute Acid} \rightarrow \text{Salt} + \text{Hydrogen gas} \]
\[ \text{Zn(s)} + 2\text{HCl(aq)} \rightarrow \text{ZnCl}_2\text{(aq)} + \text{H}_2\text{(g)} \]
C) Hydrogen gas (H₂) is generally evolved when a metal reacts with a dilute acid. This is a classic single displacement reaction where a more reactive metal displaces hydrogen from the acid.
The question asks to identify the gas evolved when dilute sulphuric acid reacts with sodium carbonate, which subsequently turns lime water milky. This is a classic chemical reaction involving an acid and a carbonate, producing a specific gas that has a characteristic test.
Identify the reactants: Dilute sulphuric acid (\(\text{H}_2\text{SO}_4\)) and sodium carbonate (\(\text{Na}_2\text{CO}_3\)).
Recall the general reaction of an acid with a carbonate: When an acid reacts with a metal carbonate, it typically produces a salt, water, and carbon dioxide gas.
General equation:
\[ \text{Acid} + \text{Metal Carbonate} \rightarrow \text{Salt} + \text{Water} + \text{Carbon Dioxide} \]
Write the specific chemical equation for the given reaction:
\[ \text{H}_2\text{SO}_4 \text{(aq)} + \text{Na}_2\text{CO}_3 \text{(aq)} \rightarrow \text{Na}_2\text{SO}_4 \text{(aq)} + \text{H}_2\text{O} \text{(l)} + \text{CO}_2 \text{(g)} \]
From the equation, it is clear that carbon dioxide (\(\text{CO}_2\)) gas is evolved.
Recall the test for carbon dioxide gas: Carbon dioxide gas turns lime water (a solution of calcium hydroxide, \(\text{Ca(OH)}_2\)) milky due to the formation of insoluble calcium carbonate (\(\text{CaCO}_3\)).
\[ \text{CO}_2 \text{(g)} + \text{Ca(OH)}_2 \text{(aq)} \rightarrow \text{CaCO}_3 \text{(s)} \downarrow + \text{H}_2\text{O} \text{(l)} \]
The white precipitate of calcium carbonate is what causes the milky appearance.
Conclusion: The gas evolved is carbon dioxide, which is known to turn lime water milky.
Correct Option: D) Carbon dioxide (CO₂)
A) Sulphur dioxide (SO₂) — Sulphur dioxide is produced when sulphites react with acids, or during the combustion of sulphur. While it can also turn lime water milky (forming \(\text{CaSO}_3\)), it is not the gas produced from the reaction of sulphuric acid with sodium carbonate.
B) Hydrogen (H₂) — Hydrogen gas is typically produced when reactive metals react with acids (
This question asks about the products formed when dilute hydrochloric acid reacts with zinc oxide. This is a classic acid-base reaction, specifically between an acid and a metal oxide. Metal oxides are generally basic in nature, and zinc oxide is an amphoteric oxide, meaning it can react with both acids and strong bases. When it reacts with an acid, it behaves as a base.
Correct Option: B) Zinc chloride (ZnCl₂) and water: ZnO + 2HCl → ZnCl₂ + H₂O
The question asks why dilute acids conduct electricity. Electrical conductivity in solutions typically depends on the presence of mobile charge carriers. We need to evaluate how acids behave in water to determine if they produce such carriers.
Therefore, the presence of these mobile ions is the reason dilute acids conduct electricity.
D) They ionise completely or partially in water, producing H⁺ ions (and corresponding anions) that carry electric current. This statement accurately describes the process. Strong acids ionize completely, while weak acids ionize partially, but both produce ions that conduct electricity.
The question asks about the reaction of dry HCl gas with dry litmus paper. To understand this, we need to recall the fundamental principle that acids exhibit their acidic properties (like changing litmus paper color) only when they are in an aqueous solution, meaning they need water to ionize and produce hydrogen ions (\(H^+\) or \(H_3O^+\)).
C) No change in colour (dry HCl does not ionise without water and cannot affect litmus)
This option correctly explains that the absence of water prevents the ionization of dry HCl gas, thus it cannot exhibit acidic properties and will not change the color of dry litmus paper.