How would you determine the acidity or measure of being acidic of the following samples: Hydrochloric Acid, Acetic Acid and Citric Acid?
Answers
Answer:A pH value is a number, usually between 0 and 14, that represents the acidity or basicity of a solution. The “pH” is always written with a lowercase “p” and an uppercase “H”, which stands for “power of hydrogen.” pH values are related to hydrogen ion ( H+ ) concentrations.
The mathematical relationship between pH and H+ is described by the equation
pH=−log(H+)(5.1)
There is an inverse relationship between pH and H+ ion concentration (in brackets, expressed in units of molarity, M). As the H+ concentration decreases, the pH value increases, and vice versa. When the pH value is a whole number (e.g. pH 7), the number is equal to the negative exponent of the H+ ion concentration.
pH value=X⟶[H+]=10−XM(5.2)
So for pH 7, the H+ ion concentration is 10-7 M.
The pH values of everyday chemicals typically range from pH 0 to pH 14. Values between 0 and 7 indicate an acidic solution. Values between 7 and 14 indicate a basic solution. A pH of exactly 7 indicates that a solution is neutral, neither acidic or basic. Pure water is usually pH 7.
The pH scale is shown below.
Chem9_exp8.png
The lower the pH value, the more acidic the solution; the higher the pH value, the more basic the solution. Basic solutions are also called alkaline solutions. It should be noted that the pH scale does extend beyond 0 and 14. Strong laboratory acids typically have pH values less than 0 (negative pH values) and strong laboratory bases typically have pH values greater than 14. Thus, they are considerably more dangerous.
The concept of pH is widely used in all areas of science including agriculture, biology, engineering and medicine. Many commercial products use pH as an advertisement tool, such as shampoo and water; more recently, food and drink of certain pH has been touted as more healthful.
A pH indicator is a substance that, when a small amount of it is added to a solution of unknown pH, will change its color. This is a way to determine pH of a solution visually. The indicator used in this lab will be obtained from a natural source, red cabbage. Cabbage indicator yields a particular color depending on the pH of the solution. pH indicators are a good way to easily and quickly show the approximate pH by color when compared to a standard. An everyday example where a pH indicator is used is for testing a water sample from a swimming pool.
While pH indicators are useful for qualitative purposes, when an exact quantitative value is needed, a pH meter is used. A laboratory pH meter typically has a special probe capped with a membrane that is sensitive to H+ ion concentrations. The meter reading shows an exact pH value of the solution probed.
Explanation: