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TEAS 7 Science C2 Acids, Bases and Salts Why is KOH a strong alkali?......

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.

More Questions on TEAS 7 Science

  • Q #1: When copper sulfate is made by reacting copper oxide with sulfuric acid, the acid is heated. Why?

    A. To increase the rate of reaction

    B. To decrease the rate of reaction

    C. To prevent the formation of byproducts

    D. To decrease the energy of activation

    Answer Explanation

    A) To increase the rate of reaction (Correct Answer): Heating the sulfuric acid increases the kinetic energy of the particles, leading to more frequent and energetic collisions between the reactant particles. This, in turn, increases the rate of reaction between copper oxide and sulfuric acid, facilitating the production of copper sulfate.

    B) To decrease the rate of reaction: Heating typically increases the rate of reaction by providing more energy for particles to overcome the activation energy barrier. Decreasing the temperature would slow down the reaction, which is not the intended outcome in this scenario.

    C) To prevent the formation of byproducts: While heating may influence the selectivity of reactions and the formation of byproducts in some cases, the primary purpose of heating sulfuric acid in this context is to increase the rate of reaction rather than to prevent the formation of byproducts.

    D) To decrease the energy of activation: Heating increases the energy of particles, helping them overcome the energy barrier required for the reaction to occur. Therefore, heating sulfuric acid would increase the energy of activation rather than decrease it.

  • Q #2: Strong bases are:

    A. Strong electrolytes

    B. Weak electrolytes

    C. Nonelectrolytes

    D. Also strong acids

    Answer Explanation

    a. Strong electrolytes (Correct Answer): Strong bases completely dissociate into ions in solution, making them strong electrolytes. They conduct electricity well due to the presence of a high concentration of ions.

    b. Weak electrolytes: Strong bases, unlike weak bases, completely dissociate in solution, resulting in a high concentration of ions. Therefore, they are considered strong electrolytes, not weak electrolytes.

    c. Nonelectrolytes: Nonelectrolytes do not ionize in solution and do not conduct electricity. Strong bases, however, ionize completely in solution, making them strong electrolytes.

    d. Also strong acids: Strong bases and strong acids are two distinct types of compounds. Strong bases ionize completely in solution to produce hydroxide ions, while strong acids ionize completely to produce hydrogen ions (H+). They are not the same.

  • Q #3: What is the Brønsted-Lowry definition of an acid and base?

    A. Acids are electron donors and bases are electron acceptors.

    B. Acids are proton donors and bases are proton acceptors.

    C. Acids are proton acceptors and bases are proton donors.

    D. Acids are compounds that increase the concentration of hydroxide ions in solution and bases are compounds that increase the concentration of hydrogen ions in solution.

    Answer Explanation

    A) Acids are electron donors and bases are electron acceptors: This statement describes the Lewis definition of acids and bases, which focuses on the transfer of electron pairs, rather than the Brønsted-Lowry definition, which involves the transfer of protons.

    B) Acids are proton donors and bases are proton acceptors. (Correct Answer): According to the Brønsted-Lowry definition, an acid is a substance that donates a proton (H+ ion), while a base is a substance that accepts a proton.

    C) Acids are proton acceptors and bases are proton donors: This statement incorrectly describes the roles of acids and bases according to the Brønsted-Lowry definition. Acids donate protons, while bases accept protons.

    D) Acids are compounds that increase the concentration of hydroxide ions in solution and bases are compounds that increase the concentration of hydrogen ions in solution: This statement does not accurately represent the Brønsted-Lowry definition. Acids and bases are defined based on their behavior regarding proton transfer, not changes in ion concentration.

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