A sample of air was bubbled into water. The PH of the water slowly changed from 7 to 6. Which of the following gases in the samples caused the change?

The pH of water is a measure of its acidity, with a lower pH indicating a more acidic solution and a higher pH indicating a more basic solution. When the pH of water changes from 7 to 6, it means that the water has become more acidic. Carbon dioxide (CO\(_2\)) is known to dissolve in water and form carbonic acid, which is a weak acid. This weak acid will increase the acidity of the water, causing its pH to decrease. Oxygen and nitrogen are not acidic gases and would not cause the pH of the water to change. Carbon(II) oxide, also known as carbon monoxide, is a toxic gas that can interfere with the ability of the blood to transport oxygen, but it is not an acidic gas and would not cause the pH of the water to change. Therefore, the gas that caused the change in the pH of the water from 7 to 6 is carbon dioxide (CO\(_2\)).