Tough Chemistry Quiz For Students

The correct answer is H. Hydrogen is represented by the symbol H in the periodic table. It is the lightest and most abundant element in the universe.

Sodium is actually one of the most reactive elements. It is a highly reactive metal that readily reacts with water and oxygen in the air. It is known to be so reactive that it must be stored in oil to prevent it from reacting with moisture in the air. Therefore, the statement that sodium is the least reactive is incorrect.

Aluminum is not the most reactive metal. In fact, it is known for its low reactivity compared to other metals. It forms a protective oxide layer on its surface, which prevents further reactions with oxygen in the air. This oxide layer helps to make aluminum highly corrosion-resistant. Therefore, the statement "Aluminum is the most reactive metal" is false.

Barium salts are generally soluble in water, except for barium sulfates. This means that when barium salts are added to water, they dissolve and form a homogeneous solution. However, when barium sulfate is added to water, it does not dissolve and remains as a solid. This is due to the low solubility of barium sulfate in water. Therefore, the statement "Most barium salts are soluble except barium sulfates" is true.

In the given diagram, the pH range for methyl orange is shown as 3.1-4.4, while the pH range for methyl red is shown as 4.4-6.2. Looking at the table, we can see that the pH of solution Z is 5.3, which falls within the pH range of methyl red but not within the pH range of methyl orange. Therefore, only methyl red will be yellow in solution Z, making the correct answer "Z only".

Acids are substances that can donate hydrogen ions (H+) to other substances. When acids dissolve in water, they release H+ ions, which can react with other substances. This ability to donate H+ ions is what defines acids. Therefore, the correct answer is "Donor of H+ ion."

Ethanoic acid, also known as acetic acid, is likely to have a pH of 4.5. This is because ethanoic acid is a weak acid, meaning it does not completely dissociate in water. It only partially ionizes, resulting in a lower concentration of hydrogen ions (H+) and therefore a higher pH compared to strong acids like hydrochloric acid and sulfuric acid. Nitric acid is a strong acid, so it would have a lower pH than ethanoic acid.

Copper is classified as a very unreactive metal because it has a low reactivity with other substances. This means that it does not easily undergo chemical reactions or form compounds with other elements or compounds. Copper is often used in electrical wiring and plumbing because of its unreactive nature, as it is less likely to corrode or react with the substances it comes into contact with. Therefore, the statement "Copper is very unreactive" is true.

Barium sulfate is insoluble in water because it has a low solubility product constant (Ksp). When it is dissolved in water, it forms solid particles that do not dissociate into ions. This low solubility is due to the strong attraction between the barium cations and sulfate anions, which prevents them from separating and dissolving in the water. As a result, barium sulfate precipitates out of the solution, making it insoluble. In contrast, barium nitrate, barium chloride, and copper sulfate are all soluble in water and dissociate into ions when dissolved.

Copper sulfate and sodium chloride cannot be prepared by reacting a metal with an acid because copper and sodium are not metals that react with acids to form salts. Copper sulfate is prepared by reacting copper oxide or copper carbonate with sulfuric acid, while sodium chloride is a compound formed by the reaction of sodium hydroxide with hydrochloric acid.