14. a student mixes strawberry koolaid and water. a ph meter is used to measure ph of 5.4. what kind of solution is strawberry koolaid?
15. in the koolaid mixture, what must there be more of, hydrogen ions or hydroxide ions?
16. a student adds an alka-seltzer to the koolaid and stirs. the ph meter now reads 8.3. what was released by the alka-seltzer tablet to cause this change?
17. bromthymol blue is a chemical indicator that is blue in basic and neutral solutions, and turns greenish and then yellow as the solution becomes more and more acidic. fill in what color you think bromthymol blue would be in each of the situations in the chart.
| situation | ph | bromthymol blue indicator color |
| --- | --- | --- |
| water directly out of tap | ph = 7.2 | |
| ph after exhaled air is blown through a straw into water for 5 min. | ph=5.1 | |
| ph after a snail has lived in water for three days | ph=5.8 | |
| ph with 2ml of bleach added to the water | ph=9.4 | |
| ph with instant coffee added to the water | ph=5.0 | |
| ph after an aquatic plant is grown in water for three days in bright sunlight | ph=7.7 | |

a. what effect does carbon dioxide have on tap water?
b. is bleach an acid or a base?
c. is coffee an acid or a base?

Question

14. a student mixes strawberry koolaid and water. a ph meter is used to measure ph of 5.4. what kind of solution is strawberry koolaid?
15. in the koolaid mixture, what must there be more of, hydrogen ions or hydroxide ions?
16. a student adds an alka-seltzer to the koolaid and stirs. the ph meter now reads 8.3. what was released by the alka-seltzer tablet to cause this change?
17. bromthymol blue is a chemical indicator that is blue in basic and neutral solutions, and turns greenish and then yellow as the solution becomes more and more acidic. fill in what color you think bromthymol blue would be in each of the situations in the chart.
| situation | ph | bromthymol blue indicator color |
| --- | --- | --- |
| water directly out of tap | ph = 7.2 |  |
| ph after exhaled air is blown through a straw into water for 5 min. | ph=5.1 |  |
| ph after a snail has lived in water for three days | ph=5.8 |  |
| ph with 2ml of bleach added to the water | ph=9.4 |  |
| ph with instant coffee added to the water | ph=5.0 |  |
| ph after an aquatic plant is grown in water for three days in bright sunlight | ph=7.7 |  |

a. what effect does carbon dioxide have on tap water?
b. is bleach an acid or a base?
c. is coffee an acid or a base?

Accepted Answer

### Question 14
# Brief Explanations:
The pH scale ranges from 0 - 14. A pH less than 7 indicates an acidic solution, pH = 7 is neutral, and pH greater than 7 is basic. The strawberry Kool - aid solution has a pH of 5.4, which is less than 7.
# Answer:
Strawberry Kool - aid is an acidic solution.

### Question 15
# Brief Explanations:
In an aqueous solution, the concentration of hydrogen ions ($H^+$) and hydroxide ions ($OH^-$) determines the pH. For an acidic solution (pH < 7), the concentration of hydrogen ions is greater than the concentration of hydroxide ions. Since the Kool - aid mixture has a pH of 5.4 (acidic), there must be more hydrogen ions.
# Answer:
There must be more hydrogen ions.

### Question 16
# Brief Explanations:
The initial pH of the Kool - aid solution was 5.4 (acidic). After adding the alka - seltzer tablet, the pH became 8.3 (basic). Alka - seltzer tablets contain substances (like bicarbonates) that can release hydroxide ions ($OH^-$) or react with hydrogen ions to increase the pH. The alka - seltzer tablet released hydroxide ions (or a basic substance) which reacted with the acidic components of the Kool - aid, increasing the pH.
# Answer:
The alka - seltzer tablet released hydroxide ions (or a basic substance) to cause the pH change.

### Question 17 (Table Filling)
For each situation, we use the properties of bromothymol blue: blue in basic and neutral solutions, greenish then yellow as acidity increases.
- Water directly out of tap (pH = 7.2): Since pH is close to neutral (7) and slightly basic, the color is blue.
- pH after exhaled air is blown through a straw into water for 5 min (pH = 5.1): pH is acidic, so the color is yellow.
- pH after a snail has lived in water for three days (pH = 5.8): pH is acidic, so the color is yellow (or greenish - yellow, but more towards yellow as pH is 5.8 which is acidic).
- pH with 2 mL of bleach added to the water (pH = 9.4): pH is basic, so the color is blue.
- pH with instant coffee added to the water (pH = 5.0): pH is acidic, so the color is yellow.
- pH after an aquatic plant is grown in water for three days in bright sunlight (pH = 7.7): pH is slightly basic, so the color is blue.

### Question 17a
# Brief Explanations:
When carbon dioxide ($CO_2$) is blown into tap water, it dissolves and reacts with water to form carbonic acid ($H_2CO_3$: $CO_2 + H_2O
ightarrow H_2CO_3$). Carbonic acid is an acid, so it increases the concentration of hydrogen ions in the water, thereby decreasing the pH of the tap water (making it more acidic).
# Answer:
Carbon dioxide dissolves in tap water to form carbonic acid, which decreases the pH of the tap water (makes it more acidic).

### Question 17b
# Brief Explanations:
The pH of bleach - water solution is 9.4, which is greater than 7. Substances with a pH greater than 7 are basic. So bleach is a base.
# Answer:
Bleach is a base.

### Question 17c
# Brief Explanations:
The pH of the water with instant coffee added is 5.0, which is less than 7. Substances with a pH less than 7 are acidic. So coffee is an acid.
# Answer:
Coffee is an acid.

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QUESTION IMAGE

Question

Explanation:

Question 14

Answer:

Question 15

situation	ph	bromthymol blue indicator color
ph after exhaled air is blown through a straw into water for 5 min.	ph=5.1
ph after a snail has lived in water for three days	ph=5.8
ph with 2ml of bleach added to the water	ph=9.4
ph with instant coffee added to the water	ph=5.0
ph after an aquatic plant is grown in water for three days in bright sunlight	ph=7.7