PH Analysis

Place these unknown pH test papers in order from most acidic to most alkaline.

• Paper D, paper C, paper B, paper A

• Paper B, paper A, paper C, paper D

• Paper C, paper D, paper A, paper B

• Paper D, paper C, paper A, paper B

Answer explanation

The acids are on the low-numbered, red end of the pH color chart, and the bases are on the high-numbered, blue-green end of the chart. The order from acidic to alkaline for the given pH test strips is orange, yellow, green, blue, or in other words, D, C, A, B.

Tags

NGSS.MS-PS1-2

A new mild dish detergent is being tested before putting it on the market. If the new detergent were tested with 0-14 pH test paper, the test strip would most likely turn what color?

• 2.3

• 5.6

• 8.2

• 13.2

Answer explanation

Soap and detergent products usually have a pH between 7.0 and 14, depending on how strong the cleaning product needs to be. Shampoos and mild hand soaps are mildly alkaline, while oven cleaners and ammonia are strong alkaline substances.

Tags

NGSS.MS-PS1-2

Chemicals in the air can combine with rain to produce acid rain, which is harmful to the environment. Which of these is most likely to be the pH of acid rain?

• 0

• 4

• 10

• 14

Answer explanation

Acid rain must be more acidic than pure water, so its pH must be less than 7. That eliminates answer choices C and D. If acid rain had a pH of 0, it would be like a pure acid falling from the sky, and that would destroy many things when it landed. The only pH that makes sense for acid rain is 4. That is acidic enough to be harmful, but not so acidic that it would destroy much of life as we know it. (According to the website of the Environmental Protection Agency, or EPA, most acid rain that falls in the United States has a pH of about 4.3.)

Tags

NGSS.MS-PS1-2

Based on the materials measured in the Gizmo, what is the most likely pH of apple juice?

• 0.3

• 3.9

• 8.4

• 11.7

Answer explanation

Substances with a pH above 7 are often used as cleaning agents and have a bitter taste, like soap. Substances with an acidic pH (below 7) are often sour in taste. Many fruit juices are mildly acidic, including apple juice. A pH below 1 represents a very strong acid that would cause serious harm if ingested.

Suppose you have already compared the pH values of two substances using 0-14 paper. When would a follow-up test using 4.5-7.5 paper be most helpful?

• when both substances had a pH value of about 3 on the 0-14 paper

• when both substances had a pH value of about 6 on the 0-14 paper

• when both substances had a pH value of about 9 on the 0-14 paper

• when one substance had a pH value of about 5 and the other substance had a pH value of about 7 on the 0-14 paper

Answer explanation

Using 4.5-7.5 paper would be most helpful when the pH values are fairly close together, and when the pH values are between 4.5 and 7.5. If both substances had a pH value of about 3 or about 9 on the 0-14 paper, those values are outside the range of the 4.5-7.5 paper, so you can eliminate answer choices A and C. If one substance has a pH of about 5 and the other has a pH of about 7, you can tell those apart easily enough with the 0-14 paper. If the pH values of both substances are around 6, that is the perfect time to use the more precise 4.5-7.5 paper.

Which term best describes a solution with a pH of 5?

• acidic

• neutral

• basic

• colorless

Answer explanation

A solution with a pH of 5 is acidic. A pH below 7 is acidic. A pH of 7 is neutral. Above 7 is basic.

Which pH indicates a basic solution?

• 1

• 5

• 7

• 12

Answer explanation

A pH of 7 is neutral. A pH ranging from 7.1 to 14 indicates a basic solution.

Which of these pH numbers indicates the highest level of acidity?

• 5

• 8

• 10

• 12

Answer explanation

7 is the pH of a neutral solution. The pH of an acid ranges from 1, indicating a very strong acid, to 6.9, indicating a very weak acid.

An acidic solution could have a pH of

• 7

• 10

• 3

• 14

Answer explanation

A pH of 7 is neutral. An acidic solution must have a pH lower than 7.

Base your answer to the question on the graph and on your knowledge of biology. The graph illustrates a single species of bacteria grown at various pH levels. Which statement is supported by data from this graph?

• All species of bacteria can grow well at pH 7.

• This type of bacterium would grow well at pH 7.5.

• This type of bacterium would grow well at pH 2.

• Other types of bacteria can grow well at pH 4.

Answer explanation

This graph is for one and only one species of bacteria. The graph shows the most growth at a pH of 8 and good growth at a pH of 7. Thus, it is reasonable that, at a pH of 7.5, this type of bacteria would grow well.

Tags

NGSS.MS-LS1-5