A student determines that a substance must be either a neutral or an acid after using phenolphthalein as an indicator. The phenolphthalein must have done what in the presence of the solution?

The phenolphthalein remained clear.

The phenolphthalien turned red.

The phenolophthalein turned magenta.

The phenolphthalien remained blue.

The Baseics Of PH

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| By Kshu121

Kshu121

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Quizzes Created: 1 | Total Attempts: 223

Questions: 10 | Attempts: 229 | Updated: Mar 20, 2023

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This quis was designed to test your knowledge of the South Caroline Seventh grade Science standards on pH.

Questions and Answers

1.

____________ are substances that have a sour taste, are corrosive to metals, and have a pH less than 7.
- A.
  
  Acids
- B.
  
  Bases
- C.
  
  Neutrals
- D.
  
  Solutions
Correct Answer
A. Acids

Explanation
Acids are substances that have a sour taste, are corrosive to metals, and have a pH less than 7. They release hydrogen ions when dissolved in water, which gives them their acidic properties. Acids can react with metals to produce hydrogen gas and can also react with bases to form salts and water. Examples of common acids include vinegar (acetic acid), lemon juice (citric acid), and stomach acid (hydrochloric acid).

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2.

________ are substances that have a bitter taste, a slippery feel, and a pH greater than 7.
- A.
  
  Acids
- B.
  
  Bases
- C.
  
  Neutrals
- D.
  
  Solutions
Correct Answer
B. Bases

Explanation
Bases are substances that have a bitter taste, a slippery feel, and a pH greater than 7. They are the opposite of acids, which have a sour taste and a pH less than 7. Bases can neutralize acids and are commonly found in household products such as soap and baking soda. They are also important in chemistry and can be used in various reactions and processes.

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3.

A substance is determined to have a pH of 3. This substance must be a(n) ________.
- A.
  
  Acid
- B.
  
  Base
- C.
  
  Neutral
- D.
  
  Solution
Correct Answer
A. Acid

Explanation
A substance with a pH of 3 indicates that it has a high concentration of hydrogen ions (H+). This high concentration of H+ ions is characteristic of acids, as acids release H+ ions when dissolved in water. Therefore, the substance with a pH of 3 is an acid.

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4.

Frederick tests the pH of an unidentified substance and finds its pH to be 11. This substance must be a(n) ________.
- A.
  
  Acid
- B.
  
  Base
- C.
  
  Neutral
- D.
  
  Solution
Correct Answer
B. Base

Explanation
Based on the pH value of 11, which is greater than 7, it can be concluded that the unidentified substance is a base. Bases have pH values greater than 7, indicating that they are alkaline substances.

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5.

Pure water is a ________ because it has a pH of 7.
- A.
  
  Acid
- B.
  
  Base
- C.
  
  Neutral
- D.
  
  Solution
Correct Answer
C. Neutral

Explanation
Pure water is considered neutral because it has a pH of 7. The pH scale measures the acidity or alkalinity of a substance, with values below 7 indicating acidity, values above 7 indicating alkalinity, and a pH of 7 indicating neutrality. Since pure water has a pH of 7, it is neither acidic nor alkaline, making it neutral.

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1
0
6.

A student uses blue litmus paper to determine the relative pH of a substance. The litmus paper turns red when it comes in contact with the substance. The student can determine that this substance is a(n) ________.
- A.
  
  Acid
- B.
  
  Base
- C.
  
  Neutral
- D.
  
  Solution
Correct Answer
A. Acid

Explanation
The blue litmus paper turns red when it comes in contact with the substance, indicating that the substance is acidic. Blue litmus paper is used to test for acidity, as it turns red in the presence of an acid.

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7.

A student determines that a solution is an acid after using litmus paper in the solution. The litmus paper must have turned what color in order for the students to draw this conclusion?
- A.
  
  Blue
- B.
  
  Magenta
- C.
  
  Orange
- D.
  
  Red
Correct Answer
D. Red

Explanation
The litmus paper must have turned red in order for the student to conclude that the solution is an acid. Litmus paper is a pH indicator that changes color depending on the acidity or alkalinity of a solution. In this case, the red color indicates that the solution is acidic.

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8.

A student determines that a substance must be either a neutral or an acid after using phenolphthalein as an indicator. The phenolphthalein must have done what in the presence of the solution?
- A.
  
  The phenolphthalien turned red.
- B.
  
  The phenolophthalein turned magenta.
- C.
  
  The phenolphthalien remained blue.
- D.
  
  The phenolphthalein remained clear.
Correct Answer
D. The phenolphthalein remained clear.

Explanation
The correct answer is that the phenolphthalein remained clear. This indicates that the substance is either neutral or acidic. If the phenolphthalein turned red or magenta, it would indicate that the substance is basic. If the phenolphthalein remained blue, it would indicate that the substance is strongly basic.

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9.

Phenolphthalein turns bright magenta in the presence of an unknown substance. The substance must be a ______________.
- A.
  
  Strong acid
- B.
  
  Strong base
- C.
  
  Weak acid
- D.
  
  Weak base
Correct Answer
B. Strong base

Explanation
Phenolphthalein is a pH indicator that changes color in the presence of acids and bases. It is colorless in acidic solutions and turns bright magenta in the presence of strong bases. Therefore, if phenolphthalein turns bright magenta in the presence of an unknown substance, it indicates that the substance is a strong base.

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10.

The closer a substance's pH is to 7 the _________ the pH of the substance is.
- A.
  
  Heavier
- B.
  
  Lighter
- C.
  
  Stronger
- D.
  
  Weaker
Correct Answer
D. Weaker

Explanation
The closer a substance's pH is to 7, the weaker the pH of the substance is. This is because pH measures the acidity or alkalinity of a substance on a scale of 0 to 14, with 7 being neutral. As the pH value deviates from 7 towards either end of the scale, the substance becomes stronger in terms of its acidity (pH below 7) or alkalinity (pH above 7). Therefore, when a substance's pH is closer to 7, it indicates a weaker level of acidity or alkalinity.

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The "Base"Ics Of pH

____________ are substances that have a sour taste, are corrosive to metals, and have a pH less than 7.

________ are substances that have a bitter taste, a slippery feel, and a pH greater than 7.

A substance is determined to have a pH of 3. This substance must be a(n) ________.

Frederick tests the pH of an unidentified substance and finds its pH to be 11. This substance must be a(n) ________.

Pure water is a ________ because it has a pH of 7.

A student uses blue litmus paper to determine the relative pH of a substance. The litmus paper turns red when it comes in contact with the substance. The student can determine that this substance is a(n) ________.

A student determines that a solution is an acid after using litmus paper in the solution. The litmus paper must have turned what color in order for the students to draw this conclusion?

A student determines that a substance must be either a neutral or an acid after using phenolphthalein as an indicator. The phenolphthalein must have done what in the presence of the solution?

Phenolphthalein turns bright magenta in the presence of an unknown substance. The substance must be a ______________.

The closer a substance's pH is to 7 the _________ the pH of the substance is.