:pH is a measure of how acidic or basic a substance is. The pH scale ranges from:

A. 0–7

B. 7–14

C. 0–14

D. 1–10

Answer Explanation:

A. 0–7: This range corresponds to acidic solutions on the pH scale. A pH value below 7 indicates acidity.

B. 7–14: This range corresponds to basic solutions on the pH scale. A pH value above 7 indicates alkalinity.

C. 0–14 (Correct Answer): The pH scale ranges from 0 to 14, covering the entire spectrum of acidity and alkalinity. A pH value of 7 is considered neutral, while values below 7 indicate acidity and values above 7 indicate alkalinity.

D. 1–10: This range does not encompass the full range of the pH scale. The pH scale extends beyond 10 for alkaline solutions and below 1 for highly acidic solutions. Therefore, this choice is incorrect.

Therefore, the Correct Answer is C.

Q #1: What is produced when an acid reacts with a metal?

A. Salt and water

B. Carbon dioxide and water

C. Oxygen gas and water

D. Salt and hydrogen

Answer Explanation

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

B) Carbon dioxide and water: This reaction occurs when an acid reacts with a metal carbonate, not a metal. 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. Metal reactions with acids usually produce hydrogen gas along with a salt.

D) Salt and hydrogen (Correct Answer): When an acid reacts with a metal, hydrogen gas is produced along with a salt. The metal displaces hydrogen ions from the acid, forming a salt, while hydrogen gas is released as a byproduct of the reaction.
Q #2: 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 #3: Why is NaCl neutral?

A. Because it contains both hydrogen and hydroxide ions in equal amounts

B. Because it contains hydrogen ions (H+) and hydroxide ions (OH-) in equal amounts

C. Because it does not contain any hydrogen or hydroxide ions

D. Because it dissociates completely in water

Answer Explanation

Rationale for each choice:

A) Because it contains both hydrogen and hydroxide ions in equal amounts: This statement is incorrect. NaCl (sodium chloride) does not contain hydrogen or hydroxide ions. It dissociates into sodium ions (Na+) and chloride ions (Cl-) in water, not hydrogen or hydroxide ions.

B) Because it contains hydrogen ions (H+) and hydroxide ions (OH-) in equal amounts: This statement is incorrect. NaCl does not contain hydrogen or hydroxide ions. In aqueous solution, NaCl dissociates into sodium ions and chloride ions, not hydrogen or hydroxide ions.

C) Because it does not contain any hydrogen or hydroxide ions (Correct Answer): NaCl is a neutral compound composed of sodium ions (Na+) and chloride ions (Cl-). It does not contain any hydrogen or hydroxide ions, so it is neutral in aqueous solution.

D) Because it dissociates completely in water: NaCl does dissociate in water, but its dissociation does not involve the generation of hydrogen or hydroxide ions. It dissociates into sodium ions and chloride ions, which do not contribute to the pH of the solution. Therefore, the completeness of dissociation does not determine its neutrality.

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:pH is a measure of how acidic or basic a substance is. The pH scale ranges from:

More Questions on TEAS 7 Science

Q #1: What is produced when an acid reacts with a metal?

Answer Explanation

Q #2: What do plants use the nitrogen in fertilizers for?

Answer Explanation

Q #3: Why is NaCl neutral?

Answer Explanation

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