Why is KOH a strong alkali?

A. Because it reacts vigorously with acids

B. Because it forms a basic solution when dissolved in water

C. Because in solution it fully dissociates into K+ and OH-

D. Because it forms insoluble precipitates with metal cations

Answer Explanation:

A) Because it reacts vigorously with acids: While KOH does react with acids to form salts and water, the strength of an alkali is not solely determined by its reactivity with acids.

B) Because it forms a basic solution when dissolved in water: This statement is true, but it does not fully explain why KOH is considered a strong alkali. Many compounds can form basic solutions when dissolved in water.

C) Because in solution it fully dissociates into K+ and OH- (Correct Answer): KOH is considered a strong alkali because it fully dissociates in aqueous solution into potassium ions (K+) and hydroxide ions (OH-). This dissociation leads to a high concentration of hydroxide ions in solution, making it strongly alkaline.

D) Because it forms insoluble precipitates with metal cations: This statement describes the formation of insoluble hydroxide precipitates when alkali solutions are added to solutions of metal salts. However, it does not fully explain why KOH itself is considered a strong alkali.

Therefore, the Correct Answer is C.

Q #1: What do plants use the nitrogen in fertilizers for?

A. To provide energy for photosynthesis

B. To build cellulose in cell walls

C. To build amino acids and proteins

D. To regulate water uptake

Answer Explanation

A) To provide energy for photosynthesis: While nitrogen is essential for various metabolic processes in plants, it is not directly involved in providing energy for photosynthesis. Instead, plants use sunlight to convert carbon dioxide and water into glucose during photosynthesis.

B) To build cellulose in cell walls: Nitrogen is not directly involved in the synthesis of cellulose, which is primarily composed of glucose units. Cellulose synthesis mainly relies on carbon and hydrogen, which are obtained from carbon dioxide and water during photosynthesis.

C) To build amino acids and proteins: Plants use nitrogen from fertilizers to synthesize amino acids and proteins. Nitrogen is a crucial component of amino acids, the building blocks of proteins, which are essential for plant growth, development, and various physiological processes.

D) To regulate water uptake (Correct Answer): Nitrogen plays a role in regulating various physiological processes in plants, including water uptake. It affects the osmotic potential of plant cells and helps regulate the movement of water and nutrients within the plant.
Q #2: What do bases react with?

A. Acids to produce salts and water

B. Salts to produce acids and water

C. Water to produce acids and salts

D. Neither acids, salts, nor water

Answer Explanation

A) Acids to produce salts and water (Correct Answer): Bases react with acids to form salts and water. This reaction is a common characteristic of bases, where they accept protons (H+) from acids to form water and salts.

B) Salts to produce acids and water: Bases typically do not react with salts to produce acids and water. The reaction between a base and a salt is not a common reaction in chemistry.

C) Water to produce acids and salts: Bases do not react with water to produce acids and salts. Bases can ionize in water to produce hydroxide ions (OH-) but do not typically react with water to produce acids and salts.

D) Neither acids, salts, nor water: Bases do react with acids to form salts and water, making choice D incorrect. Bases do not react with salts or water to produce acids, salts, or water.
Q #3: What is produced when an acid reacts with a metal oxide?

A. Salt and water

B. Carbon dioxide and water

C. Oxygen gas and water

D. Hydrogen gas and water

Answer Explanation

A) Salt and water (Correct Answer): When an acid reacts with a metal oxide, a salt and water are typically produced. The metal in the metal oxide combines with the acid to form a salt, and water is produced as a byproduct of the reaction.

B) Carbon dioxide and water: This reaction occurs when an acid reacts with a metal carbonate, not a metal oxide. When carbonates react with acids, carbon dioxide gas is produced along with water and a salt.

C) Oxygen gas and water: This reaction is not typical when an acid reacts with a metal oxide. Metal oxides generally do not produce oxygen gas when reacting with acids.

D) Hydrogen gas and water: This reaction occurs when an acid reacts with a metal, not a metal oxide. When metals react with acids, hydrogen gas is typically produced along with water and a salt.

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Why is KOH a strong alkali?

More Questions on TEAS 7 Science

Q #1: What do plants use the nitrogen in fertilizers for?

Answer Explanation

Q #2: What do bases react with?

Answer Explanation

Q #3: What is produced when an acid reacts with a metal oxide?

Answer Explanation

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