14251506 acid base and salt

8/9/2019 14251506 Acid Base and Salt

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SCIENCE

PHYSIC

BIOLOGY

CHEMISTRY

ACID

BASE

SALT

Example :HCl = Hydrochloric Acid

NaOH = Sodium HydroxideCaS = Calcium Sulfide


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T he aim this subject, you can :To classify substance having acid, base, and salt characteristic.

To distinguish acid, base, and salt by using an appropriate

indicator. And to use a simple tool to determine the acidityof a certain substance.


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According to Arrhenius, an element atom interacting with other elementatoms can release or gain a number of electrons. T he element atom releasingelectrons will be positively charged negatively. T he element atoms which areelectrically charged (positively of negatively) are called ions. T he examples of ionsamong others, are hydrogen ion (H +), sodium ion (Na +), chloride ion (Cl -), etc. As aresult, the definition of acid according to Arrhenius is as follows.

Acid is a substance that releases hydrogen ions (H +) when it is dissolved inwater.

Based on the definition of acid according to Arrhenius, then when an acidcompound is dissolved in water the hydrogen ions (H +) and negative ion will beformed according to the following reaction.


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1. Hydrochloric acid = HCl H + + Cl -2. Sulfuric acid = H 2SO4 2H + + SO 42-

3. Phosphoric acid = H 3PO 4 3H + + PO 43-

NAME CHEMICAL FORMULA


Hydrofluoric acid HF Phosphorous acid H 3PO 3Sulfuric acid H 2SO4 Acetic acid CH 3COOH

Hydrochloric acid HCl Carbonic acid H 2CO 3Nitric acid HNO 3 Oxalic acid H 2C2O 4Chromic acid H 2CrO 4 Nitrous acid HNO 2Phosphoric acid H 3PO 4 Chloric acid HClO 3

Any example of acid


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G enerally, acids or substance containing acid have the characteristicsas follows :

T hey are corrosive, meaning they can destroy other materials, includingmetals and marble.

T hey can react with metals and they produce hydrogen gas (H 2).T hey have sour taste.T hey can change the color of other substances, such as litmus paper,

essence of hibiscus, essence of red cabbage, etc.


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Acids are easily found in everyday life, it is :In milk, there is lactic acid; In citrus fruits, there is citric acid; in grapes,

there is tartaric acid; etc.In human body, there is acid which functions as a constructive substance

that is protein, protein is an acid formed from amino acid.

In food there is vinegar or acetate acid.etc


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You have washed clothes using soap, havent you? W hen we wash clothes or dishes using soap, our brushing the

clothes or dishes which have been smeared with soap willproduce foam?


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Base is a substance that releases hydroxide ions (OH -) when it isdissolved in water.

Based on the base definition above, then when a base is dissolvedin water, hydroxide ions (OH -) and positive ions are formed according tothe following reaction.

1. Sodium hydroxide = NaOH Na + + OH -2. Ammonium hydroxide = NH 4OH NH 4+ + OH -

3. Potassium hydroxide = Ca(OH) 2 Ca2+ + 2(OH) -


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M agnesiumhydroxide

M g (OH) 2 Barium hydroxide Ba (OH) 2

Zinc hydroxide Zn (OH) 2 Calcium hydroxide Ca (OH) 2Iron (II) hydroxide Fe (OH) 2 Ammonium hydroxide NH 4OH

Iron (III) hydroxide Fe (OH) 3 Potassium hydroxide KOH

Aluminum hydroxide Al (OH) 3 Sodium hydroxide NaOH

Any example of bases


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Similar to acid, bases also come in solids, liquids andgases. Some bases are also used by humans, but some others areharmful and poisonous. Hence, we had better learn thecharacteristics of bases. G enerally, bases or substance containing

base have characteristics as follows :T hey are caustic, meaning they can damage our skin or othermaterials.

T hey feel smooth on our hand. It is because they can reactwith fat on our skin and form a soap layer.

T hey have bitter taste.T hey can change the color of other substance, such as litmus

paper, essence of hibiscus, essence of red cabbage, etc.However, the change in color produced by the base is different

from that produced by acid.


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Bases are easily found in everyday life, it is :In limestone, there is calcium hydroxide; In cleaning liquids,

there is ammonium hydroxide; in medicines for heartburn,there is aluminum hydroxide and magnesium hydroxide; etc.

In agriculture for the feedstock in fertilizer manufacturingcontaining calcium hydroxide.

etc


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W e have know that both acid and base are able to change thecolor of other substances. T he substances the color of which can changewhen they interact or react with acid or base are called acid-base

indicators.In a chemical laboratory, acid-base indicators which are usually

used are artificial indicators and natural indicators. T he following areexplanations about those indicators.


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T he scientist made litmus paper. T he litmus paper is a kind of substanceprepared from a kind of lichen (Roccella tinctoria). Litmus paper which iscommonly used in chemical laboratories now is prepared in the form of paper.

As an acid-base indicator, litmus has some advantages among other, are asfollows :

T he color of litmus can change quickly when it react with both acid and base. T hechange of color produced by the litmus paper can be seen clearly. Litmus becomesred in acid solution and it be comes blue in base solution.

Litmus is difficult to react with oxygen in the air, so it is durable.Litmus is absorbable by paper, so it used in the form of litmus paper (to make the

substance easily permeates).Besides litmus, there are also many other artificial acid-base indicators in a

chemical laboratory, among others, are phenolphthalein, methyl red andbromothymol blue.

Phenolphthalein in acid solution does not change in color, while in basesolution it become red. M ethyl red in acid solution has red color, while in basesolution it becomes yellow.


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ACID-BASE INDICATOR

INDICATOR IN BASE IN ACID

Litmus Blue RedM ethyl Red Yellow Red

Phenolphthalein Red Uncolored

Bromothymol Blue Blue Yellow


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Besides the artificial indicators, such as litmus, phenolphthalein,methyl red, bromothymol blue, we can also identify acid or base by usingnatural indicator, such as hibiscus, turmeric, red cabbage, and some otherkinds of plants.


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To determine the value of pH of a substance, we cannot use alitmus paper, phenolphthalein, methyl red, and other indicators as we havediscussed in the previous subchapter. T he value of pH can be determinedusing a universal indicator indicating various colors for each value of pH.T he universal indicator is equipped with a color map, so we can determinethe value pH based on the color in the map.

Besides we use the universal indicator, to determine the value of pH of a substance, we also can use an instrument of pH directly by a digitalscreen on the instrument.


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If an acid solution and base solution are mixed in a vessel, the H + ion (fromacid) will react with the OH - ion (from base) to form water. T he reaction betweenH + ion and the OH - ion can be written as follows.

T he reaction between acid and base is called the neutralization reaction. It isbecause besides water, the product of reaction between acid and base is a neutralsubstance, that is a substance which is not acidic nor basic. T he neutral substancemeant is salt. Because the neutralization reaction can produce salt, then this reaction

also know by the term of salting reaction. Simply, the neutralization reaction orsalting reaction can be written as follows.


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A simple example of the salting reaction is reaction betweenhydrochloric acid (HCl) and sodium hydroxide (NaOH) which formssodium chloride (table salt) and water.

Because in this nature there are many acids and also bases, then of course the table salt is not the only the example of salt. T his means, in this

nature there are many kinds salt. Among others are calcium chloride(CaCl 2), potassium chloride (KCl), magnesium fluoride ( M gF2), zinc sulfate(ZnSO 4), barium sulfate (BaSO 4), sodium sulfide (Na 2s), and calcium sulfide(CaS).


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Unlike acid and base, salt in the form of solid (powder), liquid(solution), or gas always consists of positive and negative ions.

Besides being produced from the reaction between acid and base,salt is also produced from other reactions. T he followings are reactionswhich can produce salt.

1. Base + acid oxide salt + water2. Acid + base oxide salt + water3. Acid oxide + base oxide salt4. M etal + acid salt + hydrogen gas (H 2)


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Basically, the salting (neutralization) reaction is very useful forhuman life. T he excessive production of stomach acid causing heartburn canbe neutralized using bases of M g (OH) 2 or Al (OH) 3. Soil which is too acidicand not good for any plant, can be neutralized using the base, thatsubstance which can damage our teeth and cause a bad smell. M oreover,

there are more other salting reactions which are useful for us.


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14251506 acid base and salt

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