: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: A universal indicator has the ability to indicate the full range of pH values on the pH scale by color changes. Acids change the color of universal indicator towards:

A. Yellow, green, and blue colors.

B. Green, blue, and purple colors.

C. White, grey, and black colors.

D. Yellow, orange, and red colors

Answer Explanation

A. Yellow, green, and blue colors: This sequence of colors does not represent the typical color changes observed in universal indicator when exposed to acidic solutions. Universal indicator typically changes from green/blue in neutral solutions to yellow/orange/red in acidic solutions.

B. Green, blue, and purple colors: Purple is not typically observed in the color changes of universal indicator in acidic solutions. Universal indicator usually transitions from green/blue in neutral solutions to yellow/orange/red in acidic solutions.

C. White, grey, and black colors: These colors are not typically observed in the color changes of universal indicator. Universal indicator undergoes a series of color changes from green/blue to yellow/orange/red in acidic solutions.

D. Yellow, orange, and red colors. (Correct Answer): Universal indicator typically changes from green/blue in neutral solutions to yellow/orange/red in acidic solutions. This sequence of colors represents the typical color changes observed in universal indicator when exposed to acidic solutions.
Q #2: What is produced when an acid reacts with a metal hydroxide?

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 hydroxide, a salt and water are typically produced. The metal in the metal hydroxide 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 hydroxide. 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 hydroxide. Metal hydroxides 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 hydroxide. When metals react with acids, hydrogen gas is typically produced along with water and a salt.
Q #3: Why is dry hydrogen chloride gas not acidic?

A. Because it does not react with water

B. Because it does not contain hydrogen ions (H+)

C. Because it contains hydrogen ions but not chloride ions (Cl-)

D. Because hydrogen is bonded to chlorine in dry HCl and not dissociated

Answer Explanation

A) Because it does not react with water: While dry hydrogen chloride gas does not react with water, the absence of this reaction does not inherently determine its acidity. Acidity is determined by the presence of hydrogen ions in solution.

B) Because it does not contain hydrogen ions (H+): Dry hydrogen chloride gas does not contain free hydrogen ions, which are characteristic of acidic solutions. However, the absence of hydrogen ions alone does not explain why dry hydrogen chloride gas is not acidic.

C) Because it contains hydrogen ions but not chloride ions (Cl-): Dry hydrogen chloride gas does not contain free chloride ions, but the presence of hydrogen ions is crucial for acidity. However, the absence of chloride ions alone does not fully explain why dry hydrogen chloride gas is not acidic.

D) Because hydrogen is bonded to chlorine in dry HCl and not dissociated (Correct Answer): Dry hydrogen chloride gas does not dissociate into hydrogen ions (H+) and chloride ions (Cl-) because there is no water present to facilitate dissociation. Therefore, it does not exhibit acidic properties in the absence of dissociation.

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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: A universal indicator has the ability to indicate the full range of pH values on the pH scale by color changes. Acids change the color of universal indicator towards:

Answer Explanation

Q #2: What is produced when an acid reacts with a metal hydroxide?

Answer Explanation

Q #3: Why is dry hydrogen chloride gas not acidic?

Answer Explanation

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