Properties of Acids
- Sour Taste: Acids typically have a sour taste, as seen in lemons (citric acid) and vinegar (acetic acid). Most sour foods contain weak acids.
- Reaction with Metals: Many acids react with metals causing corrosion, such as sulfuric acid in car batteries. However, some metals like silver, gold, and platinum do not react with acids.
- Litmus Paper Test: Acids turn blue litmus paper red. (Remember: Blue turns Red in Acid)
Common Acids and Their Strength
- Strong Acids: Nitric acid (HNO3), sulfuric acid (H2SO4), and hydrochloric acid (HCl) are strong acids that fully ionize in water. For a deeper understanding of these acids, check out Understanding Oxyacids: Formation, Naming, and Formulas Explained.
- Weak Acids: Acetic acid (found in vinegar) and formic acid are weak acids that partially ionize. They contain a carboxylic group (-COOH).
- Industrial and Biological Importance: Sulfuric acid is widely produced industrially and is present in car batteries. Hydrochloric acid is found in the human stomach aiding digestion. For more on the classification of elements related to these acids, see Understanding the Classification of Elements and Periodic Properties in Chemistry.
Properties of Bases
- Physical Characteristics: Bases feel slippery and have a bitter taste.
- Litmus Paper Test: Bases turn red litmus paper blue.
- Common Strong Bases: Sodium hydroxide (NaOH), potassium hydroxide (KOH), and calcium hydroxide (Ca(OH)2) fully ionize in water.
- Weak Bases: Ammonium hydroxide (aqueous ammonia) and sodium bicarbonate partially ionize.
Uses of Acids and Bases
- Antacids: Bases like sodium bicarbonate are used to neutralize excess stomach acid (hydrochloric acid) to relieve heartburn. However, frequent use is discouraged as it does not treat underlying causes. For a comprehensive guide on titration, which is essential for understanding acid-base reactions, refer to Understanding Titration: A Comprehensive Guide to Determining Solution Concentration.
- Cleaning Agents: Many bases, including soaps, serve as effective cleaning agents.
Ionization and Strength
- Strong Acids and Bases: Fully dissociate in water, producing ions exclusively (e.g., NaOH → Na+ + OH-).
- Weak Acids and Bases: Partially dissociate, existing as both molecules and ions in solution (e.g., NH4OH ⇌ NH4+ + OH-). For a deeper dive into enzyme properties that can relate to acid-base interactions, see Understanding the Properties of Enzyme Active Sites.
Understanding these properties helps in identifying acids and bases, their behavior in reactions, and their practical applications in daily life and industry.
Some properties of acids. Acids have sour taste. For example, in this lemon, it is sour because it has an acid called
citric acid and also vinegar. Vinegar have acidic acid. Most sour foods, even sour candies have some acids, but they
are weak acids. In foods, we do not have strong acid. Another property of acid is they react with metals. Not all metals,
many metals. That's why in car batteries you might have seen this corrosion because batteries have sulfuric acid and
sulfuric acid reacts with metal and it corrods. Here another example of using acid to dissolve metal. I think in a
movie or somewhere they use acid to break out of the gel but not all of the acid silver gold platinum these and some
other metals do not react with acids. And another property is there's something called litmos papers. We use
litmos papers to check the acidity or basicity. There are two types of litmos papers. Blue Litmas paper and red litmos
paper. Blue becomes red when there's an acid. Just remember B. Blue becomes red when there is an acid. So opposite is
red litmus. You will see in a minute. Red litmus become blue when there's a base. If you remember one thing, it's
easy to remember the other one. So these are some of the common acids we use. Uses I don't want you to remember, but
it's good to remember because they are everyday chemicals. What I want you to remember is these three acids nitric
sulfuric and HCl and also I want you to know that they are strong acids and also I want to remember acetic acid is a weak
acid that's acid in vinegar and these acids we don't use it very often but of course there are uses acid is a good
acid to remember we consider it as a moderately strong probably HCL is the most used example in our class and in
our labs and this is the acid actually in our stomach this is sulf sulfuric acid and this is the mostly produced
chemical in USA. You can see H2SO4 there are two hydrogen atoms here and you can see this whole molecule is a
covealent molecule. It is not ionic but we know that in aquous medium it can release H+. There are two hydrogen's
connected to this oxygen and these are ionizable hydrogen. They can ionize in water. There are two of them. But in
nitric there's only one ionizable hydrogen. Therefore in water it will give only one hydrogen ion. Acidic acid
is different because this is a weak acid. And also if you see this hydrogen also connected to oxygen. There's a
group in most of the weak acids called CO caroxyic group. We call these acids as caroxilic acids. So acidic is one of
the caroxilic acid. Formic acid. This is another caroxilic acid. Now the bases some characteristics of bases. They are
slippery. There are many bases we use including soap as cleaning agents. And if you ever taste it, it's not sour. It
has bitter taste. And we can use litmus papers to identify bases. In this case, red becomes blue in bases. And most of
the bases have hydroxide ions in water. So these are the common bases. I want you to remember these three. Sodium
hydroxide, potassium hydroxide and calcium hydroxide. I want you to know that they are strong because they are
fully ionized in water. So ammonium hydroxide is aquous ammonia and also these are weak bases except this sodium
bicarbonate or sodium hydrogen carbonate the same thing except that all other bases we see here have O just like acids
have hydrogens generally bases have hydroxide ions you can see that magnesium hydroxide sodium bicarbonate
some of the uses are anti- acid probably you might have seen in the store anti- acid tablets Because sometimes you might
have problems with acidity in your stomach. So if you use these ant acids, these bases can react with acid in the
stomach, hyaluronic acid in the stomach and it can neutralize it. You will not feel the pain of that acid. But we
cannot use anti- acids just to cure the disease. The reason you have more acid in the stomach is some other disease.
That disease is not going to be cured by these chemicals. Therefore, it is very bad to use antiac acid over and over to
relieve your pain. We need to find the exact reason for that. I just told you to discourage taking anti- acid in a
consistent basis. Strong acids and strong bases are completely ionized in water. But weak acids are weak bases do
not. They are partially ionized in water. Most of the molecules of weak acids are weak bases are present as
molecules in water, not as ions. That's why they are called fake acids and bases. Sodium hydroxide in water, it
dissociates into sodium plus and O minus ions. So this is fully dissociate. All sodium hydroxide dissociate into sodium
and hydroxide ions. There are no sodium hydroxide formula units in water. Everything is dissociated. Same with
hydrochloric acid HCl. When you put in water, we do not see any HCl molecules. We see only H+ and Cl minus ions. Those
are strong acids and strong bases. But for weak acids or weak bases, let's say ammonium hydroxide or ammonia in water,
they give ammonium plus an hydroxide ion. But this is not fully dissociated. This is partially dissociated. That
means you have both ammonium ion and hydroxide ion and also you have ammonium hydroxide. So the meaning of weak is it
is not fully dissociated. That's what this double arrow means.
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