#### Acidity Ph And Indicators

1
2
3
4
5
6

A sample of normal rainwater has a pH value of 5.6 due to dissolved carbon dioxide gas from the atmosphere. Acid rain is formed when other gases, such as sulfur dioxide, dissolve in rainwater, which can result in lake water with a pH value of 4.6. The equation below represents the reaction of water with SO2(g).

7

In a laboratory investigation, an HCl(aq) solution with a pH value of 2 is used to determine the molarity of a KOH(aq) solution. A 7.5-milliliter sample of the KOH(aq) is exactly neutralized by 15.0 milliliters of the 0.010 M HCl(aq). During this laboratory activity, appropriate safety equipment is used and safety procedures are followed.

8

A student is to determine the concentration of an NaOH(aq) solution by performing two different titrations. In a first titration, the student titrates 25.0 mL of 0.100 M H2SO4(aq) with NaOH(aq) of unknown concentration.

In a second titration, the student titrates 25.0 mL of 0.100 M HCl(aq) with a sample of the NaOH(aq). During this second titration, the volume of the NaOH(aq) added and the corresponding pH value of the reaction mixture is measured. The graph below represents the relationship between pH and the volume of the NaOH(aq) added for this second titration.

9

Carbon dioxide is slightly soluble in seawater. As carbon dioxide levels in the atmosphere increase, more CO2 dissolves in seawater, making the seawater more acidic because carbonic acid, H2CO3(aq), is formed.

Seawater also contains aqueous calcium carbonate, CaCO3(aq), which is used by some marine organisms to make their hard exoskeletons. As the acidity of the sea water changes, the solubility of CaCO3 also changes, as shown in the graph below.

10
11

Vinegar is a commercial form of acetic acid, HC2H3O2(aq). One sample of vinegar has a pH value of 2.4.

12

The hydrangea is a flowering plant. The color of the flowers it produces can change depending on the pH value of the soil in which the plant grows. Adding aluminum sulfate makes the soil more acidic and adding calcium hydroxide makes the soil more basic.

A student performed an experiment by varying soil pH and recording the color of the flowers. The following table summarizes the results of the experiment.

13