Indicators: Salts & pH Video Lecture | Advance Learner Course: Science Class 9

Ans. Salts are chemical compounds composed of a positive ion (cation) and a negative ion (anion) that are formed when an acid reacts with a base. When dissolved in water, salts can affect pH by either increasing or decreasing it, depending on the nature of the ions present. For example, salts formed from strong acids and strong bases are neutral and do not affect pH, while salts formed from weak acids or weak bases can make a solution more acidic or alkaline.

Ans. The pH of a solution can change when a salt is added depending on the nature of the salt's ions. If the salt is formed from a strong acid and a strong base, it will not affect the pH and the solution will remain neutral. However, if the salt is formed from a weak acid and a strong base, the solution will become more alkaline. Conversely, if the salt is formed from a strong acid and a weak base, the solution will become more acidic. The pH change is due to the dissociation of the salt into its respective ions and their interactions with water molecules.

Ans. Yes, salts can be used to adjust the pH of a solution. By choosing the appropriate salt with the desired ions, it is possible to increase or decrease the pH of a solution. For example, if a solution is too acidic, a salt formed from a weak base and a strong acid can be added to increase the pH. Conversely, if a solution is too alkaline, a salt formed from a weak acid and a strong base can be added to decrease the pH. However, it is important to consider the potential side effects and limitations of using salts to adjust pH, as excessive amounts can lead to undesired consequences.

Ans. pH can significantly affect the solubility of salts. Some salts are more soluble in acidic solutions, while others are more soluble in alkaline solutions. This is because the concentration of hydrogen ions (H+) or hydroxide ions (OH-) in the solution can influence the ability of the salt to dissolve. For example, certain metal hydroxide salts are more soluble in alkaline solutions due to the presence of excess hydroxide ions, while some metal carbonate salts are more soluble in acidic solutions due to the presence of carbonic acid. Understanding the pH-dependent solubility of salts is important in various industries, such as pharmaceuticals and agriculture.

Ans. pH indicators are substances that change color depending on the pH of a solution. They can be used to determine the acidity or alkalinity of a solution by observing the color change. Each pH indicator has a specific range of pH values in which it undergoes a color change. For example, litmus paper turns blue in alkaline solutions and red in acidic solutions. By comparing the color change of an indicator with a standard color chart or pH scale, the pH of a solution can be estimated. pH indicators are commonly used in laboratories, water testing, and quality control processes to assess the acidity or alkalinity of a solution.