The understandable notes- Acid, Base and Salts, Class 10, Part- 2
Reaction of metallic oxide with Acids
When a metallic oxide reacts with acid then it forms salt and water. The basic reaction can be written as
As this reaction is similiar to reaction of bases with acids, metallic oxides are also known as basic oxides.
( Ab agla reaction aata hai acid ka metallic oxides ke sath. Metal oxide jaise ki sodium oxide wagera. To jab bhi acid kisi metallic oxide ke sath react krti hai tab salt or water ki formation hoti hai. Aur yehi same products form hote hai jab acid ka reaction kisi base ke sath hota hai. Iska matlab ye hai ki metallic oxides ek base ki tarah kaam krti hai aur inhi wajah se inhe basic oxides bhi kehte hai. Ab inke do teen example fekh lo mai niche likh deta hu.)
REACTION OF NON- METALLIC OXIDE WITH BASE
When a non metallic oxide reacts with a base, it forms salt and water. This reaction is similar to the reaction of base with acid and hence non metallic oxides are considered as acidic in nature and also called as acidic oxides. The basic reaction can be written as
( Ab metaliic oxides kebaad bari aati hai nonmetallic oxides ki. To ye to common sense ki baat hai ki non metallic oxide nature mai metallic oxide ke opposite hongi. Ab metallic oxide to nature mai basic hoti hai to non metallic oxide nature mai acidic hongi. Ab is se ye chiz bhi clear hai ki agar inka reaction kisi base ke sath jaye to ye acid ki tarah hi react krengi aur same products form kregi jo ki acid aur base ke reaction se hote hai. To bas ye bhi salt aur water ki formation krengi. Ab inke reaction thode se complicated hote hai jo is part mai padhne ki jarurat nahi hai par jaha jarurat padegi waha likh dunga. )
ACIDS AND BASES IN AQUEOUS MEDIUM
In water, acids dissociate into ions. They dissociate either completely or partially depending on their strength and form hydrogen ions (H⁺). However, the hydrogen ion cannot exist independently, so it combines with a water molecule (H₂O) to form a hydronium ion (H₃O⁺). Thus, the hydrogen ion is always represented as the hydronium ion.
The reaction of hydrochloric acid in water is given below:
Similarly the reaction of sulphuric acid with water is given below:
( Ab ye to maine pehle part ke starting mai bhi bataya tha ki acids water mai react hokr hydrogen ion banati hai. Bas ye hi baat yaha par bhi likhi hui hai. Lekin acids bhi strong or weak hoti hai jo hume aage padhna hai. Jo strong acid hoti hai vo completely dissociate ho jati hai par jo waek acid hoti hai vo completely dissociate nahi ho pati. Ab konsi acid strong hai aur konsi waek hai ye hum ph wale topic mai padhenge. Aur ek aur jaroori baat, dekho hydrogen ion ki form mai hi separate hoga, aur hydrogen ion ka simple sa matlab ye hai ek proton. Ye to sabko pata ho hoga hydrogen ka atomic number one hota hai aur isme ek proton aur ek electron hi present hota hai to jab ek electron nikal gaya to bacha kya, sirf ek proton aur isi wajah se ye independentlyexist nahi krta. Balki ye combine hota hai water ke molecule ke sath aur banata hai hydronium ion jo maine upar likha tha. To jab bhi hydrogen ion ko represent kro to hydronium ion ki for mai hi kiya kro. Chalo dekhte hai ki bases kya krte hai pani pani hokr.)
When bases are dissolved in water, they dissociate to form hydroxide ions (OH⁻). They can dissociate completely or partially, depending on their strength. Some dissociation reactions of bases are given below:
(Ab jab bases ko water mai dissolve kiya jata hai to vo bhi acids ki tarah hi dissociate ho jate hai bas fark itna hai ki vo dissociate hokr hydrogen ion ki jagah hydroxide ions release krte hai. Ab inke bhi do char reaction likh ditlye inhe padh lena aur ab jo mai niche bataunga vo jaroor padh lena kyunki question kai baar yhi se aata hai.)
Dissociation reactions involve the formation of cations and anions. Therefore, acids and bases in water do conduct electricity. The extent of dissociation also depends on the concentration of the reactants. For example, when a sodium hydroxide (NaOH) solution reacts with carbon dioxide (CO₂), the following reactions take place:
1. When NaOH is present in excess (strong base):
2. When NaOH is present in limited amounts (weak base):
From these reactions, we can conclude that dissociation reactions depend on the concentration of the reactants. Additionally, when an acid like HCl is boiled, it forms HCl gas, which only contains molecules of acid. Since litmus paper changes color in the presence of ions, the HCl gas will not turn blue litmus paper red because it does not contain free H⁺ ions until it dissolves in water.
(Ab dissociation reaction mai ions ki formation hoti hai aur ions ki foramtion ki wajah se electricity conduct kr pana possible ho jata hai. Isi liye jab bhi hum acids aur bases ko pani mai dissolve krte hai tab vo solution electricty ke conductor ki tarah kaam krta hai. Aur agar pure acid bhi ho tab electrictiy conduct nahi ho pati kyonki pure acid mai koi ion wagera nahi hote. Haan to agar ye pucha jaye ki acids aqueous medium mai electricty kyo conduct krti hai ti likh aana ki pani mai acid dissociate hokr ions ki formation krti hai aur isi wajah se electricty conduct ho pati hai. Aur ye jo dissociation reaction hai ye concentration par bhi depend krta hai. Jaise ki upar mene do reaction likhe hai inhe dekh lena. Jab NaOH strong tha tab sodium carbonate ki formation hui aur jab NaOH weak tha yani ki kam amount mai present tha tab sodium bi carbonatr ki formation hui. To ye choti choti chizo par bade bade questions bhi aa jate hai. Aur is part ke baad ek question bhi dekha maine ncert mai to socha ki uska answer bhi likh deta hu. Dekho koi bhi indicator kisi chemical change ko detect krke hi colour change krta hai. Dubara se bata raha hu chemical change. Ab chemical change ka matlab yaha par formation of ion hai baki aur bhi ho sakte hai. To jab HCl gas ki form dry litmus ke contact mai asti hai tab koi ion to form hua hi nhi hota. Are agar pani ko boil kroge to water vapour banega na koi hydrogen gas to nahi ban jayegi. Isi tarah HCl liquid se gas ban jayegi to ek physical change banega na ki chemical change. Bas isi liye litmus rang nahi badalta.)
The process of dissolving an acid or a base in water is highly exothermic, meaning it releases a significant amount of heat. This process is called the dilution of the acid or base because it reduces the concentration of ions per unit volume. When mixing acid with water, it should always be done with constant stirring. If water is added directly to concentrated acid, the heat generated can cause the acid to splash out of the container, and the high temperature may even break the container. Therefore, in laboratory settings, dilute acids are typically used for experiments instead of concentrated acids. The same precautions apply to bases as well.
( Ab dekhte hai ki acid or base ko pani me milane par kya hota hai. To ye reaction highly exothermic hota hai, matlab jab ye reaction hota hai tab heat release hoti hai. Ab kisi bhi acid ya base ko paani mai milane ko dilution bolte hai. Dilution is liye kyonki ye acid ya base ko concentration ko kam kr deta hai. To ab mai batata hu ki ise kra kaise jata hai. To ek baat yaad rakhna )
pH- How strong are acids and bases
pH is a measure of the hydrogen ion (H⁺) concentration in a solution. It indicates whether a substance is acidic, basic, or neutral.
The p in pH stands for ‘potenz’ in German,
meaning power. On the pH scale we can measure pH generally from 0 (very acidic) to 14 (very alkaline). Higher the hydronium ion concentration, lower is the pH value.
( Ab bari aati hai acid aur base ki strength ki. Ab ye kaise pata kre ki koi substance acidic hai ya basic, ab tum taste krke to nahi bataoge ki ye to khatta hai to ye acidic hoga ya ye to kadwa hai to basic hoga. Ab iske liye aata hai pH yani ki power ya fir potential of hydrogen. Ab pH scale par 0 se lekar 14 tak marking hoti hai. Ab is chiz ka bilkul dhyan rakhna ki jitna hydrogen ions ki concentration badhegi utna pH value kam hogi aur jitna hydroxide ion ki value badhegi utna ph value badhegi. Ab ye to humne padha hi hai ki acid hydrogen ion ko dissociate krta hai aur base hydroxide ion ko. To jaha par pH ki value jyada aaye to vo substance basic hai aur jaha par pH ki value kam hai vo substance acidic hai. Ye upar to thoda sa likha hua hai par topic samajhne wala hai.)
A universal indicator is a mixture of several indicators that shows different colors at different pH values, helping to determine the strength of acids and bases. It provides a more accurate measurement of pH compared to single indicators like litmus.
( Ab aata hai univeral indicator jo ki hume batata hai ki koi bhi substance acidic, basic hai ya fir neutral hai. Ab univeral indicator har pH value par alag colour show krta hai. Kitne pH par konsa colour show krta hai ye pata krne ki jarurat nahi hai. Ab ye indicator kafi jyada useful hai kyonki ye jyada accurate of efficient hai.)
Importance of pH in Everyday Life
- Our body works within the pH range of 7.0 to 7.8. Living organisms can survive only in a narrow range of pH change.
- When pH of rain water is less than 5.6, it is called acid rain. When acid rain flows into the rivers, it lowers the pH of the river water. The survival of aquatic life in such rivers becomes difficult.
- Most plants grow best in soil with pH between 6 to 7.5.
- Acid-loving plants (pH 4.5 - 6): Pineapple, Blueberries, Tea.
- Neutral pH plants (pH 6 - 7): Wheat, Rice, Corn, Sunflower.
- Alkaline soil plants (pH 7.5 - 8.5): Barley, Cotton, Cabbage.
- The stomach has a highly acidic pH of 1.5 to 3.5 due to the presence of hydrochloric acid (HCl), which helps in digesting proteins by activating the enzyme pepsin and killing harmful bacteria. This acidic environment is essential for breaking down food effectively. However, if stomach acid increases too much, it can cause acidity, ulcers, or acid reflux, leading to discomfort. To neutralize excess acid, antacids like milk of magnesia are used. A balanced stomach pH is crucial for proper digestion and preventing digestive disorders.
- Tooth decay happens when the pH in the mouth drops below 5.5. Tooth enamel, the hardest substance in the body, is made of calcium hydroxyapatite. It does not dissolve in water but gets damaged when the mouth becomes too acidic. Bacteria in the mouth produce acids by breaking down sugar and food particles left after eating. The best way to prevent tooth decay is to clean the mouth after meals. Toothpaste, which is usually basic, helps neutralize the acid and protect the teeth.
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