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.

Therefore, the Correct Answer is D.

Q #1: 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 #2: What ions make ethanoic acid acidic?

A. H+ ions

B. OH- ions

C. Na+ ions

D. Cl- ions

Answer Explanation

A) H+ ions (Correct Answer): Ethanoic acid (acetic acid) is acidic because it donates protons (H+) in solution, leading to the formation of hydronium ions (H3O+). This process characterizes acids.

B) OH- ions: Hydroxide ions (OH-) typically characterize bases, not acids. Ethanoic acid doesn't contain hydroxide ions.

C) Na+ ions: Sodium ions (Na+) are not responsible for the acidity of ethanoic acid. Na+ ions are typically found in salts and do not contribute to acidity.

D) Cl- ions: Chloride ions (Cl-) are not responsible for the acidity of ethanoic acid. Cl- ions are typically found in salts and do not contribute to acidity.
Q #3: What is an appropriate pH value for hydrochloric acid?

A. pH 2-4

B. pH 1-3

C. pH 0-2

D. pH 3-5

Answer Explanation

Rationale for each choice:

A) pH 2-4: While hydrochloric acid is indeed highly acidic, a pH range of 2-4 would suggest a slightly less concentrated solution. However, this range might still be appropriate for dilute or partially neutralized hydrochloric acid.

A) pH 1-3 (Correct Answer): Hydrochloric acid typically has a very low pH due to its strong acidic nature. A pH range of 1-3 is commonly observed for concentrated hydrochloric acid solutions.

C) pH 0-2: This range suggests an even stronger acidity, which could be true for very concentrated hydrochloric acid solutions, although they might not commonly occur in typical laboratory or industrial settings.

D) pH 3-5: This pH range would indicate a significantly less acidic solution compared to hydrochloric acid. Such a pH range might be more appropriate for weak acids or diluted hydrochloric acid solutions rather than the concentrated form.

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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:

More Questions on TEAS 7 Science

Q #1: Strong bases are:

Answer Explanation

Q #2: What ions make ethanoic acid acidic?

Answer Explanation

Q #3: What is an appropriate pH value for hydrochloric acid?

Answer Explanation

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