Concept about Acid – Introduction to fundamental concepts of Biological Science including the organization and common characteristics of living matters, cell structures and functions, food production by photosynthesis, harvesting energy, mechanism of cells reproduction, genetics, evolutions, and Human Biology. Introduction to general chemistry including basic concepts about matter, atomic structure, chemical bonds, gases, liquid, and solids, solutions, chemical reactions, acid, bases, and salt;
organic and biochemistry including hydrocarbons and their derivatives, carbohydrates, lipids, proteins, enzymes, vitamins, and minerals, nucleic acids; principles of physics and applications to nursing including gravity and mechanics, pressure, heat and electricity; nuclear chemistry and nuclear physics, effects of radiation on human beings, and protection and disposal. The aim of the course is to acquire knowledge and skills in general biological science, general chemistry and physics.
Concept about Acid
An acid is a chemical species that donates protons or hydrogen ions and/or accepts electrons. Most acids contain a hydrogen atom bonded that can release (dissociate) to yield a cation and anion in water. The higher the concentration of hydrogen ions produced by an acid, the higher its acidity and the lower the pH of the solution. The word acid from the Latin words acidus or acere, which mean “sour”, since one of the characteristics of acids in water is a sour taste (e.g., vinegar or lemon juice).
Summary of Acid and Base Properties
This table offers an overview of key properties of acids compared with bases:
| Property | Acid | Base |
| PH | Less than 7 | Greater than 7 |
| Litmus paper | Blue to red | Don’t change litmus, but can return acid (red) paper back to blue |
| Taste | Sour (e.g. Vinegar) | Bitter or soapy (e.g., baking soda) |
| Odor | Burning sensation | Often no odor (exception is ammonia) |
| Texture | Sticky | Slippery |
| Reactivity | Reacts with metals to produce hydrogen gas | Reacts with several fats and oils |
Definition of Acid:
Acids are most commonly used in aqueous solution although they may exist as solids, liquids of gas.
For example, Hydrogen chloride, HCI is a gas; Sulphuric acid, H2SO4, is a liquid; and Boric acid, H3BO3, is a solid.
Properties of Acids:
- ➤ Acids change the colour of litmus from blue to red.
- ➤ They convert the colour of Methyl Orange from Orange/Yellow to Pink.
- ➤ Acids turn the pink colour of Phenolphthalein to colourless.
- ➤ Acids can conduct electricity.
- ➤ Some Acids are highly corrosive in nature which means that they corrode or rust metals.
- ➤ Acids tend to evolve hydrogen gas whilst reacting with an active metal such as Zn, Mg, etc.
- ➤ They produce H+ ions when mixed with water.
- ➤ Acids lose their acidity when mixed with a base.
- ➤ When equal amounts of acid and base are combined the process of neutralization occurs and salt and water is formed,
- ➤ The pH value of acid is from 0-6. Learn the concept of pH value here.
- ➤Acids are sour in taste.
- ➤ Acids react with carbonates and hydrogen carbonates to form a salt, water, and carbon dioxide gas.
- ➤ Extremely active metals such as Potassium (K), Calcium (Ca), Sodium (Na), etc tend to explode when combined with acids.
- ➤ Weak Acids like Carbonic Acid doesn’t act with any metal at all.
- ➤ Nitric Acids doesn’t usually exhibit acidic properties, it exhibits oxidizing properties 40 instead.
- ➤ Metals that generally react with dilute acid to form salt and hydrogen are the metals which lie above hydrogen in the metal activity series.
- ➤ Acids form a salt, water and sulphur dioxide while reacting with sulphites and bisulphites
- ➤ Acids and metal sulphides form salt and hydrogen sulphide.
- ➤ They are classified on the basis of their sources, strength, concentration, the presence of oxygen and its basicity.
- ➤ The different types of acids are organic acids, mineral acids, strong acids, weak acids, concentrated acids, dilute acids, Oxy-acids, Hydracids, monobasic acids, dibasic acids, and tribasic acids.
Importance of Acids:
Some acids (inorganic and organic) are commonly used in laboratories and hospitals which are described as follows:
| Acid | Uses |
| Inorganic | |
| Hydrochloric acid | In gastric digestion of proteins. |
| Nitric acid | Coagulant in testing for albumin in die urine. |
| Hypochlorus acid | Disinfectant, antiseptic and bleaching agent. |
| Boric acid | Antiseptic for inflamed mucous membranes in the eyes nose or mouth. |
| Organic | |
| Acetic acid | Removes insoluble soaps and nits from hair. |
| Citric acid | In form of citrate of magnesium as a laxative. |
| Lactic acid | In the manufacture of yeast and cheese. |
| Salicylic acid | In the form of salicylate as an antiseptic. |
| Tartaric acid | As salt in baking powder |
Difference between Strong acid & Weak acid:
| Traits | Strong acid | Weak acid |
| Definition | Acids which are almost completely dissociated are called strong acid. | Acids which are dissociated in a very negligible amount are called weak acids. |
| Conjugate base | Weak | Strong |
| Chemical reaction | Irreversible. e.g. HNO3 -> H+ NO3- | Reversible. e.g. HCOOH -> H + HCOO |
| Examples | Usually all the inorganic acids except H2CO3 | Usually all the organic acids & H2CO3 |
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