Science Education, Science Notes: The Acid Base Chemistry

Showing posts with label The Acid Base Chemistry. Show all posts

More about salts

Explain the different products formed during electrolysis of sodium chloride (NaCl) in solution & in fused state.

Ans. i) Electrolysis of aqueous solution of NaCl when electricity is passed through an aqueous solution of sodium chloride commonly known an brine (10% NaCl), it decomposes to form sodium hydroxide. Chlorine (Cl₂) gas is liberated at anode & hydrogen (H₂) gas at cathode respectively.

2NaCl + 2H₂O -------> 2NaoH + C2 + H₂

ii) Electrolysis of fused sodium chloride : When sodium chloride is heated at high temperature, it melts. The moten state is termed as fused state. NaCl in fused state conducts electricity. During electrolysis Cl₂ (g) is liberated at anode & sodium is deposited at the cathode.

2NaCl -------> 2Na + Cl2

Give the properties of NaCl with its uses.

Ans. Properties of NaCl.

i) Impure NaCl is brown in colour known as rock salt & purified NaCl is white (colourless), crystalline ionic compound.

ii) It is soluble in water.

Uses of NaCl.

i) NaCl is an essential constituent of our daily life. It is used in food items.

ii) It is used in the preparation of baking soda (NaHCO₃) & washing soda (Na₂CO₃).

State applications of baking soda [(NaHCO₃) sodium bicarbonate]

Ans. i) Baking soda also called as sodium bicarbonate, has many appliances.

ii) It is used in the preparation of light, soft & spongy breads, cakes & dhokla.

iii) It is used to treat slightly alkaline hyperactivity, i.e. acidity in the stomoch.

iv) Its solution is used in fire, extinguishers to produce carbon dioxide & water.

How bleaching powder is prepared?

Ans. When dry slaked lime reacts with chlorine gas, it gives bleaching powder.

Ca(OH)2 + Cl₂ -------> CaOCl₂ + H2O

Slaked lime chlorine Bleaching powder

State two properties of bleaching powder.

Ans. i) Bleaching powder is a white powder with strong odour of chlorine gas.

ii) It is an oxidizing agent in many chemical reactions.

Give uses of bleaching powder (CaOCl₂)

Ans. i) Bleaching powder (CaOCl₂) is used to disinfect a place which is not clean.

ii) It is also used to disinfeet water.

iii) It is used for bleaching cotton in the textile industry, wood pulp in paper factories & washed clothes in laundry.

iv) It is used in the preparation of chloroform.

Chemical reactions, Chemical reaction, iron nail & burning candle, Iron, Ferrous chloride, Hydrogen gas, sodium hydroxide, aluminium ribbon, Slaked lime, bleaching powder, Bleaching powder, Calcium carbonate, Chlorine, Sodium carbonate, Sodium chloride, carbon dioxide universal indicator, hydrogen, PH, ion, Magnesium ribbon, Magnesium chloride, sodium carbonate, sodium chloride, Aluminum carbonate, Aluminium chloride, sodium bicarbonate, sodium chloride Copper oxide (basic oxide) Hydrochloride acid copper chloride salt The Acid Base Chemistry, Acids and Bases, Indicators, Strength of Acids & Bases, Acids, Bases & their reactivity, Ionization of Acids and Bases, Salts.Slaked lime, chlorine, Bleaching powder, baking soda, washing soda, sodium bicarbonate

Ionization of Acids and Bases

Define ionization with example.

Ans. The process in which an ionic compound separates into positive & negative ions is called ionization. OR

Formation of ions in presence of water from a substance is called ionization.

Ex. i) When HCl gas is dissolved in water, it ionizes to H⁺ & OH^- ions.

HCl + water ----> H⁺+ Cl^-

ii) When NaoH is dissolved in wter, it ionizes to Na⁺ & OH^-ions

NaOH + water ----> Na⁺+ OH^-

Explain in detail about hydronium ion.

Ans. The strength of an acid is measured in terms of the extent of ionization of the acid in aqueous solution. Higher the H⁺ ions concentration, stronger is the acid. Hydrogen ion (H⁺) does not exist alone. H⁺ ion being unstable, combines with H₂O to form hydronium ion (H₃O⁺)

HCl ----> H⁺ + Cl^-

H^+(aq) + H₂O ----> H₃O⁺

Hydroniumion.

Acids, Bases and their Reactivity

What is the action of Mg ribbon with HCl ?

Ans. Mg Ribbon on treatment with hydrochloric acid gives magnesium chloride salt with bubbles of hydrogen gas. In this reaction hydrogen is displaced by the active metal from acid.

Mg + 2HCl ----> Mg Cl₂ + H₂

Magnesium ribbon Magnesium chloride

How do metal carbonates reacts with acid ?

Ans. When a metal carbonate or metal hydrogen carbonate reacts with an acid, it forms corresponding salt & carbon dioxide gas.

i) Na₂ CO₃ + 2HCl ----> 2 NaCl + H₂O + CO_2(g)

sodium carbonate sodium chloride

ii) Al₂(CO₃) + 6 HCl ----> 2 AlCl₃ + 3H₂O + 3CO_2(s)

Aluminum carbonate Aluminium chloride

iii) NaHCO_3(s) + HCl_(aq) ----> NaCl_(aq) + H₂O_(l) + CO₂ _(g)

sodium bicarbonate sodium chloride

How do metal oxides react with acid?

Ans. When metal oxide on reaction with acid, gives corresponding salt & water. As this reaction is similar to the reaction between acid & base, it is concluded that metallic oxides are basic oxides.

Metal oxide + Acid ----> Salt + water

CuO + 2HCl ----> CuCl₂ + H₂O

Copper oxide (basic oxide) Hydrochloride acid copper chloride (salt)

How do non metallic oxides react with base?

Ans. When a non metallic oxides on reaction with base to form corresponding salt & water. As this reaction is similar to the reaction between base & acid , it is concluded that non- metallic oxides are acidic in nature.

Ca(OH)₂ + CO₂ ----> CaCO₃ + H₂O

Calcium hydroxide (base) carbon dioxide (non metallic oxide [acid]) calcium carbonate (salt)

How do acids & bases react with each other? What is the name of the process? What product is obtained out of this reaction?

Ans. i) Acids & bases react with each other with great vigour depending on their concentration & type of the acids & bases.

ii) The reactions are exothermic in nature.

iii) When acid reacts with base to form salt & water is known as neutralization.

e.g. a) HCl + NaOH ----> NaCl + H₂O

b) H₂SO₄ + 2KOH ----> K₂SO₄ + 2H₂O

Strength of Acid and Bases

Write a short notes on p^H scale (Draw a diagram)

Ans. i) p^H scale helps in measing the hydrogen ion (H⁺) concentration in a solution.

ii) The p^H scale ranges from 0 to 14.

iii) p^H value 7 represents a neutral substance i.e. neither acidic nor basic.

iv) An acidic substance has a p^H value between 0 to 7 & a basic substance with p^H value 7 to 14.

v) Lower the p^H of an acid, greater is the concentration of H⁺ ions, greater the p^H of a base, greater is the concentration of OH^-ions.

What are strong acids ? Give two examples.

Ans. When acids in aqueous solution give more number of H⁺ ions they are termed as strong acids.

ii) Sulphuric acid H₂so₄, hydrochloric acid, HCl, nitric acids HNO₃ are strong acids.

What are weak acids? Give two examples.

Ans. i) When acids in aqueous solution give less numbers of H⁺ ions, they are termed as weak acids.

ii) Ammonium hydroxide (NH₄OH), Magnesium hydroxide (Mg(OH)₂), (OH)₂ copper hydroxide Cu(OH)₂are weak bases.

How does a tooth paste help in preventing tooth decay ?

Ans. i) Tooth decay is caused by acids produced by certain bacteria that are found in our mouth. These acids corrode the tooth enamel.

ii) Toothpaste contains alkaline substances & fluoride which neutralizes the acids in mouth. This prevents corrosion of the tooth enamel.

Explain the effect of acid rain on aquatic life in a river.

Ans. i) Pure water is neutral having p^H.7

ii) Rain water reacts with carbon dioxide, Oxides of nitrogen & sulphur dioxide in the air & becomes acidic. Acid rain has p^H less than 7.

iii) When acid rainwater flows in rivers, it lowers the p^H of river water to less than 7.

iv) When plants absorb acidic water, it adversely affects their growth, flower, fruits & even their leaves.

v) Acidic water is very harmful to aquatic life e.g. fish, frogs, aquatic plants, etc.

Indicators

Define indicators. State two acid-base indicators & mention their colour change.

Ans. i) Indicators are defined as the acidic and basic nature of the compounds can also be indicated by some natural as well as chemical substances are known as indicators.

ii) Phenolphthalein & methyl orange are two acid-base indicators.

iii) Phenolphthalein is colourless in acid solution while it turns into pink colour in base solution.

iv) Methyl orange gives orange colour with acid solution & yellow colour with base solution.

Name the carboxylic acids present in

Sr.No.		Acid	Sr.No.		Acid
1.	Tamarind		1.	Milk
2.	Butter		2.	Orange
3.	Roots of Plant velerum		3.	Red ants
4.	Lemon		4.	Honey bee

Ans. 1) Tamarind – tartaric acid 2) Butter – Butyric acid

3) Roots of plant velerum – Valeric acid 4) Lemon – citric acid

5) Milk – Lactic acid 6) Orange – citric acid

7) Red ants – Formic acid 8) Honey bee – Formic acid

Explain the term olfactory indicator.

Ans. Substances whose odour changes in acidic or basic medium are called olfactory indicator.

e.g. Eucalyptus (nilgiri) Oil, Onion & clove extract.

What is universal indicator? Does Mg OH2 react with sodium hydroxide? If not, why?

Ans. i) Universal indicator is a mixture of several indicators which gives different colours at different p^H values of the p^H scale.

ii) Mg OH2 does not react with sodium hydroxide as both are bases having the same negative radical i.e. OH-

What do you understand by universal indicator?

Ans. i) Universal indicator is a mixture of several indicators.

ii) It has a very wide range and indicating p^H value almost from 0 to 14.

iii) When one or two drops of universal indicator is added to a solution it changes its colour. This colour is matched against the colour on a standard colour chart (usually given on its bottle) to find the p^H & the p^H value can be read. This indicates the strength of the solution.

iv) It is available in the form of solution or in the form of paper strips.

Write a short notes on Indicators (give suitable example)

Ans. i) The acidic & basic nature of the compounds can also be indicated by some natural as well as chemical substances. They are known as indicators.

ii) Some indicators are obtained from nature. These are called natural indicators. e.g. Litmus solution (obtained from lower plants lichen), exteracts obtained from petals of rose or hibiscus, turmeric (stem), beet root & indigo (entire plant), etc.

iii) Some manmade chemical substances are called as synthetic indicators. ex. phenolphthalein, methyl orange, eosin, etc.

iv) Indicators also indicate the p^H of a substance by its colour. Universal indicator is specially useful to show the p^H of a substance.

Acids & Bases

Question : Give two characteristics of acids & bases.

Ans : a) Characteristics of Acids:

i) Acids are sour in taste.

ii)Acids turn blue litmus red.

b) Characteristics of Bases :

i) Bases are bitter in taste.

ii) Bases turns red litmus blue.

Pages