In chemistry, chemical compounds can be differentiated into acids and bases based on various criteria like taste, dissociation of ions, chemical properties, etc. Broadly, acids and bases can be differentiated on the basis of their pH. Acids have a pH of less than 7, while bases have a pH greater than 7. In this article, we look at 15 differences between acids and bases in detail, with some examples.
Differences between acids and bases:
| Sn.O | Basis of differentiation | Acids | Bases |
| 1 | Definition by Arrhenius | Acids are chemical compounds that increase the concentration of hydronium(H3O+) ions in an aqueous solution. | Bases are chemical compounds that furnish hydroxyl (OH-) ions in an aqueous solution. |
| 2 | Definition by Brønsted-Lowry | Acids have the ability to donate a proton to another molecule in a chemical reaction. | Bases have the ability to accept a proton from a molecule in a chemical reaction. |
| 3 | Definition by Lewis | Acids have the ability to accept a pair of nonbonded electrons during a chemical reaction | Bases have the ability to donate electron pairs to another molecule during a chemical reaction. |
| 4 | pH | Less than 7 | Greater than 7 |
| 5 | Examples | Odor | Magnesium hydroxide, borax, sodium bicarbonate |
| 6 | Taste | Sour taste (warning: do not taste acids) | Bitter taste (warning: do not taste bases) |
| 7 | Odorless except for ammonia (which has a pungent odor) | Burns your nose (Warning: Never inhale acidic fumes) | Odorless except for ammonia(has pungent odor) |
| 8 | State of matter | Acids can exist as gaseous, liquid, or solids and are sticky to the touch. | Bases are mostly solid and are slippery to the touch with some exceptions. |
| 9 | Chemical formula | Most acids contain an H at the beginning for mineral acids and COOH groups at the end for organic acids | Most bases contain OH at the end |
| 10 | Disassociation | Acids have the ability to release hydrogen ions (H+) in aqueous solutions | Bases have the ability to release hydroxide ions(OH-) in aqueous solutions |
| 11 | Litmus test | It would turn litmus paper red | It would turn litmus paper blue |
| 12 | Phenolphthalein | Remains colorless with the addition of phenolphthalein | Turns pink with the addition of phenolphthalein |
| 13 | Methyl orange | Turns red with the addition of methyl orange | Turns yellow with the addition of methyl orange |
| 14 | Universal indicator | Acids are identified by shades of red and yellow color | Bases are identified by shades of blue and violet color |
| 15 | Reaction with metal | Acids react with the metals to release hydrogen gas | Bases generally do not react with metals |
Now let discuss each one of the differences in detail
The definition for acids and bases given by a Swedish chemist named Svante Arrhenius differentiates acids and bases based on the type of ions furnished in aqueous solutions. The compounds which furnish hydronium ions are termed as acids and the compounds which furnish hydroxyl ions are termed as bases.
Brønsted-Lowry differentiated acids and bases based on the ability to donate or accept a proton(H+) during a chemical reaction. Based on this differentiation, acids are chemical compounds that can donate a proton and bases are chemical compounds that can accept a proton.
Gilbert N. Lewis differentiated acids and bases on the ability to donate or accept a non-bonded pair of electrons during a chemical reaction. According to Lewis, acids are chemical compounds that can accept a non-bonded pair of electrons, and bases are chemical compounds that can donate a non-bonded pair of electrons during a chemical reaction.
Acids have a pH less than 7 up to a value of 0 and bases have a pH greater than 7 up to a value of 12. The lower the pH value, the more acidic the compound, and the greater the pH value, the more basic is the compound. For example, acetic acid has a pH of around 3-4, and sodium hydroxide has a pH of around 13-14. You can visit this link to find out the pH of common acids and bases.
Acids are sour to taste and sticky to the touch and give a burning sensation when we inhale their fumes. Bases on the other hand, are bitter to taste, soapy to touch, and are odorless (except for ammonia). Warning: Never touch, taste, or smell a chemical compound, as this can be hazardous to your health. Always wear a lab coat and gloves while handling chemicals.
Acids can be in solid, liquid, or gaseous form. For example, zeolites are solid acids, a hydrochloric acid solution is liquid, and sulfur dioxide and sulfur trioxide are acidic gases. Bases, on the other hand, are mostly solids like sodium hydroxide and aluminum hydroxide except for ammonium which is a gas.
Acids turn blue litmus paper red, turn red with the addition of methyl orange, remain colorless with the addition of phenolphthalein, and show shades of yellow and red in universal indicator solution. Bases turn red litmus paper blue, turn yellow with the addition of methyl orange, turn pink with the addition of phenolphthalein, and show shades of blue and violet in universal indicator solutions.
Acids react with metals to give hydrogen gas. For example, zinc metal reacts with hydrochloric acid to yield zinc chloride and hydrogen gas.
2Zn + 2HCl → H2 + 2ZnCl
Bases on the other hand, do not react with acids.
Mineral acids generally have a formula that starts with the hydrogen atom. For example HNO3, HCl, HF, etc. Organic acids generally have a COOH group in their formula. Bases generally have OH in their formula. For example Zn(OH)2, Cu(OH)2, LiOH, etc.
Examples of acids include citric acids, hydrochloric acids, sulfuric acids, etc. You can read our article on 100 examples of acids.
Examples of bases include sodium hydroxide, washing soda(Na2CO3), baking soda(NaHCO3), etc.
