Acid, Bases And Salts

1. Which of the following is a soluble base?

Aluminium oxide

Copper(II) oxide

Sodium hydroxide

Iron(II) hydroxide

Sodium hydroxide is a soluble base because it dissolves in water to form hydroxide ions (OH-) which can accept protons (H+) to neutralize acids.

Explanation

Sodium hydroxide is a soluble base because it dissolves in water to form hydroxide ions (OH-) which can accept protons (H+) to neutralize acids.

2. Y is heated with aqueous sodium hydroxide and ammonia gas is formed. Y is ________.

Hydrochloric acid

Copper (II) oxide

Ammonium sulphate

Sodium nitrate

When Y is heated with aqueous sodium hydroxide, it reacts to form ammonia gas. This suggests that Y contains an ammonium compound. Among the given options, ammonium sulphate is the only compound that contains ammonium (NH4+) ions. Therefore, Y is most likely ammonium sulphate.

Explanation

When Y is heated with aqueous sodium hydroxide, it reacts to form ammonia gas. This suggests that Y contains an ammonium compound. Among the given options, ammonium sulphate is the only compound that contains ammonium (NH4+) ions. Therefore, Y is most likely ammonium sulphate.

3. Which of the following statement is not true of dilute hydrochloric acid?

It liberates ammonia gas from ammonium chloride on warming

It liberates carbon dioxide from carbonates

It ionises in water to form hydrogen ions

It reacts with active metals to produce hydrogen

Dilute hydrochloric acid does not liberate ammonia gas from ammonium chloride on warming. This is because ammonium chloride is a stable compound and does not decompose into ammonia gas and hydrochloric acid upon heating.

Explanation

Dilute hydrochloric acid does not liberate ammonia gas from ammonium chloride on warming. This is because ammonium chloride is a stable compound and does not decompose into ammonia gas and hydrochloric acid upon heating.

4. Which of the following is a reaction observable from this reaction. H₂SO₄(aq) + CuCO₃(s) --> H₂O (l) + CO₂(g) + CuSO₄(aq)

An effervescence of colourless gas with a pungent smell is observed

Copper(II) carbonate reacts with the acid and disappears, forming a blue solution

Copper(II) carbonate reacts with the acid and disappears, forming a colourless solution

Copper(II) carbonate reacts with the acid and disappears, forming a pale green solution

The given reaction involves the reaction between copper(II) carbonate (CuCO3) and sulfuric acid (H2SO4). The observation of a blue solution indicates that copper(II) carbonate reacts with the acid and disappears, forming a blue solution. This is a clear indication of a chemical reaction occurring between the two compounds.

Explanation

The given reaction involves the reaction between copper(II) carbonate (CuCO3) and sulfuric acid (H2SO4). The observation of a blue solution indicates that copper(II) carbonate reacts with the acid and disappears, forming a blue solution. This is a clear indication of a chemical reaction occurring between the two compounds.

5. Which of the following is true? The strength of an acid depends on:

It's concentration

It's pH

It's solubility in water

It's degree of ionisation in water

The strength of an acid depends on its degree of ionization in water. This means that a strong acid will completely ionize in water, while a weak acid will only partially ionize. The concentration, pH, and solubility of an acid are not indicators of its strength.

Explanation

The strength of an acid depends on its degree of ionization in water. This means that a strong acid will completely ionize in water, while a weak acid will only partially ionize. The concentration, pH, and solubility of an acid are not indicators of its strength.

6. Lake Y's water has a pH value of 3. Which substance could be added in to neutralise the pH value of the acidic water present without leaving an alkaline solution.

Aqueous sodium hydroxide

Calcium carbonate

Aqueous ammonia

Acetic acid

Calcium carbonate is a basic compound that can be added to neutralize the acidic water in Lake Y. When calcium carbonate reacts with the acidic water, it releases carbon dioxide gas and forms calcium ions and bicarbonate ions. The bicarbonate ions act as a buffer, helping to maintain a neutral pH. Unlike the other options, calcium carbonate does not leave an alkaline solution because it reacts with the acid to form a neutral solution.

Explanation

Calcium carbonate is a basic compound that can be added to neutralize the acidic water in Lake Y. When calcium carbonate reacts with the acidic water, it releases carbon dioxide gas and forms calcium ions and bicarbonate ions. The bicarbonate ions act as a buffer, helping to maintain a neutral pH. Unlike the other options, calcium carbonate does not leave an alkaline solution because it reacts with the acid to form a neutral solution.

7. Which one of the following burns in air to form an oxide which, when shaken with water, gives a solution with a pH greater than 7?

Carbon

Copper

Nitrogen

Calcium

Calcium burns in air to form calcium oxide (CaO). When shaken with water, calcium oxide reacts to form calcium hydroxide (Ca(OH)2), which is a strong base. A solution with a pH greater than 7 is considered basic, so calcium is the correct answer.

Explanation

Calcium burns in air to form calcium oxide (CaO). When shaken with water, calcium oxide reacts to form calcium hydroxide (Ca(OH)2), which is a strong base. A solution with a pH greater than 7 is considered basic, so calcium is the correct answer.

8. When two liquids are mixed, a solution with a value of pH 7 is formed. Which of the following are the pH values of the two liquids.

1st: pH 5, 2nd: pH 2

1st: pH 5, 2nd: pH 12

1st: pH 6, 2nd: pH 1

1st: pH 14, 2nd: pH 7

The correct answer is 1st: pH 5, 2nd: pH 12. This is because when two liquids with different pH values are mixed, the resulting pH of the solution depends on the concentration of hydrogen ions (H+) and hydroxide ions (OH-) in the solution. A pH of 7 is considered neutral, indicating an equal concentration of H+ and OH-. A pH value below 7 indicates acidity, while a pH value above 7 indicates alkalinity. In this case, the first liquid with a pH of 5 is acidic, and the second liquid with a pH of 12 is alkaline. When mixed together, the acidity of the first liquid and the alkalinity of the second liquid neutralize each other, resulting in a pH of 7 for the solution.

Explanation

The correct answer is 1st: pH 5, 2nd: pH 12. This is because when two liquids with different pH values are mixed, the resulting pH of the solution depends on the concentration of hydrogen ions (H+) and hydroxide ions (OH-) in the solution. A pH of 7 is considered neutral, indicating an equal concentration of H+ and OH-. A pH value below 7 indicates acidity, while a pH value above 7 indicates alkalinity. In this case, the first liquid with a pH of 5 is acidic, and the second liquid with a pH of 12 is alkaline. When mixed together, the acidity of the first liquid and the alkalinity of the second liquid neutralize each other, resulting in a pH of 7 for the solution.