Define Indicators. Name Two Natural Indicators Obtained From Plants.
Indicators are substances which give different colour in acid or bases solutions. Natural indicators from plants are:
(a) Litmus,
(b) Vanilla extract.
┬а
┬а
What Are Antacids?
Antacids are mild alkalies. These are used for getting relief from acidity and indigestion and sometimes, even headache. When taken orally, it reacts with hydrochloric acid present in the stomach and reduces its strength by consuming some of it. For example, milk of magnesia is an antacid.
┬а
What Are Olfactory Indicators? Give An Example.
Olfactory indicators are substances which have different odour in acid and base solutions. For example, vanilla essence has characteristics pleasant smell in acid solution and no smell in alkali solution.
┬а
Tap Water Conducts Electricity Whereas Distilled Water Does Not. Why?
Tap water contains some impurities in the forms of salts. Due to presence of salts, it conducts electricity. Distilled water is free from all kinds of salts and hence does not conduct electricity.
┬а
While Diluting An Acid, Why Is It Recommended That The Acid Should Be Added To Water And Not Water Into The Acid?
When an acid is mixed with water, there is evolution of large amount of heat. Therefore, acid is slowly added to water. If on the other hand, water is added to acid, it might spill on your body and clothes due to explosion and evolution of sudden and large amount of heat.
┬а
What Is Meant By The Term PH Of A Solution? The PH Of Rain Water Collected From Two Cities A And B Was Found To Be 6 And 5 Respectively. The Water Of Which City Is More Acidic?
pH is a term which indicates whether a solution is acidic of basic and to what extent. Mathematically it is a measure of H+ ions concentration in water.
The rain water collected from city B is more acidic.
┬а
Tooth Enamel Is One Of The Hardest Substance In Our Body. How Does It Undergo Damage Due To Eating Chocolates And Sweets? What Should We Do To Prevent It?
Sugar present in chocolates and sweets gets broken to acids by bacteria present in the mouth. This lowers the pH in the mouth. Tooth enamel is made up of calcium phosphate, which gets corroded when the pH in the mouth is below 5.5. To prevent tooth enamel from decay, toothpaste is used because it is alkaline and neutralises the acid produced in the mouth and helps to prevent lowering of pH in mouth.
┬а
Why Are Commercial Samples Of Bleaching Powder Not Completely Soluble In Water?
Bleaching powder is soluble in water. However, commercial samples of bleaching powder contains slaked lime that does not react with chlorine gas during the manufacture of bleaching powder. The insoluble part of bleaching powder is this white solid, i.e., slaked lime.
┬а
Questions For Practice On 10th Science Chpater 2
Question 1:
What is a neutralization reaction? Give some examples.
Answer 1:
When the effect of a base is nullified by an acid and vice versa, it is called neutralization reaction. In general, a neutralization reaction is written as:
Base + Acid тАХ> Salt + Water
Examples:
(a) Aqueous solution of base, NaOH is neutralized by aqueous hydrochloric acid.
(b) Aqueous solution of sulphuric acid is neutralized by aqueous solution of sodium hydroxide.
Question 2:
An alkali is an important base used for the laboratory work. Name the base and state how it can be prepared from common salt? What is this process called?
Answer 2:
An important alkali commonly needed for laboratory work is sodium hydroxide. It can be prepared from sodium chloride by the process of electrolysis. This is called chlor-alkali process.
Electrolysis of aqueous solution of sodium chloride: When electricity is passed through an aqueous solution of sodium chloride commonly called brine, it decomposes into chloride and sodium. Sodium is collected at the cathode where it reacts with water to form sodium hydroxide. Chlorine is formed at the anode and is collected as a gas.
Cathode:
At Anode:
The overall reaction is
Questions From Board Papers
Question 1:
(a) How does baking soda helps to make cakes and bread soft and spongy? OR
Give reason: cake rise on adding baking powder.
(b) Write chemical equation for its preparation.
Answer 1:
(a) On heating , sodium bicarbonate decomposes to produce carbon dioxide. This causes biscuits and cakes etc. to expand and become light. The other constituents act as preservatives.
(b)
Question 2:
Why does bleaching powder smell strongly of chlorine?
Answer 2:
Bleaching powder smells strongly of chlorine because it slowly reacts with carbon dioxide of air to evolve chlorine gas.
Important Questions On 10th Science Chapter 2
Base + Acid тАХ> Salt + Water
What Is Meant By The Acids? Give The Properties Of Acids?
Acids are those chemical which produce hydrogen ions in its aqueous solution for example: Citric acid, sulphuric acid, hydrochloric acid etc.
Properties of Acids are
(i) It has sour in taste.
(ii) It turns blue litmus into red.
(iii) It turns methyl orange colour into red.
(iv) Acids has corrosive in nature.
┬а
What Is Meant By The Bases? Give The Properties Of Bases?
Bases are those chemical which produce hydroxide ions (OH-) in its aqueous solution for example: Sodium hydroxide, Calcium hydroxide, Magnesium hydroxide etc.
Properties of Bases are
(i) Base has bitter in taste.
(ii) Base convert red litmus into blue.
(iii) Base convert methyl orange colour into yellow.
(iv) Base convert the colour of Phenolphthalein into pink.
(v) Base does not react with metal.
(vi) Base does not react with metal carbonate and metal hydroxide carbonate due to its basic nature.
(vii) Only alkali bases are good conductor of electricity
Describe The Preparation Of Litmus Solution?
Litmus solution is a purple dye which is extracted from a plant lichen. This dye is used an indicator to tests for acids and bases. When litmus solution is neither acidic nor basic, its colour is purple. Acids change the colour of blue litmus to red. Bases changes the red colour to blue.
┬а
Tabulate A Table To Identify The Indicators Types, Colours In Acids And Bases?
Indicator Type Its Colour Acids Base
Litmus Natural Purple Red Blue
Red cabbage leave Natural Red Red Green
Flower of hydra Natural Blue Blue Pink
Phenolphthalein Synthetic Coloueless Colourless Pink
Methyl orange Synthetic Orange Red Yellow
Turmeric Natural Yellow Yellow Reddish brown
┬а
Indicators
Indicators are those which indicates that whether the given chemical is acid or base. Naturally material like red cabbage leaves, turmeric paper, coloured petals of some flowers such as Hydrangea, Petunia and Geranium also act as indicators to test for acid and base. The types of indicators are
(i) Olfactory indicator
(ii) Synthetic indicator
(iii) Natural indicator
┬а
What Happen When Acid React With Metal?
When acid react with metal it produces metal salt and hydrogen gas.
For example:
Mg + 2HCL тЖТ MgCl2 + H2
2Na + 2HCLтЖТ2NaCl +H2
┬а
What Happen When Acid React With Metal Carbonate?
Reaction of acid with metal carbonate when acid react with metal carbonate then it produces metal salt, carbon dioxide and water.
For example:
Na2Co3 +HCL тЖТ 2NaCl + Co2 + H2O
CaCo3 + HCL тЖТ CaCl2 + CO2 + H2O
┬а
Give Some Examples Of Metal Oxide With Acid?
(i) Na2O + HCL тЖТ NaCl + H2O
(ii) CaO + HCL тЖТ CaCl2 + H2O
(iii) MgO + H2SO4 тЖТ MgSO4 + H2O
When acid react with metallic oxide then it produces salt and water because of basic nature of metallic oxide.
┬а
What Happen When Acid React With Base?
When acid react with base then it produces salt and water and it is known as neutralization reaction.
For example: NaOH + HCL тЖТ NaCl + H2O
Mg(OH)2 + H2SO4 тЖТ MgSO4 + 2H2O
┬а
What Happen When Acid React With Metal Hydrogen Carbonate?
When metal hydrogen carbonate then it produces metal salt, Carbon dioxide, water.
For example:
NaHCo3 + HCL тЖТ NaCl + Co2 + H2O
Ca(HCO3)2 + 2HCLтЖТ CaCl2 +2CO2 +2H2O
┬а
The Naturally Occurring Acids
Natural source Type of Acid
Orange, Lemon Citric Acid
Apple Malic Acid
Tomato Oxalic Acid
Tamarind Tartaric Acid
Curd Lactic Acid
Vinegar Acidic Acid
Protein Amino acid
┬а
Why Acidic Food Stuff Does Not Store In Copper Or Metallic Container?
Acidic food stuff is stored in our house hold kitchen in plastic or glass container not in copper or metallic container because acid can react with these metals and can form poisonous substance.
┬а
What Do All Acids Have In Common?
All acids have hydrogen ions (H+) in common in their aqueous form.
Type of Acid:
Concentrated acid: Concentrated acid are those which contain less amount of water.
Dilute acid: Dilute acid are those which contain more amount of water.
┬а
Describe The Process Of Dissolving Acids Or Bases In Water?
When we dilute an acid with water then addition of acid in water is a correct way of dilution because when water is added into acid then exothermic reaction take place and lots of heat come out from the test tube. Due to which it can harm us while acid is added to water then endo thermic reaction take place due to assumption of heat in water.
┬а
What Do You Understand By The Amphoteric Oxide?
Amphoteric oxide are those oxides which has acidic and basic both type of character.
For example:
NaOH + Zn тЖТ Na2ZnO3 + H2O
┬а
What Do You Understand By The Ph Scale And What Is The Important Use Of This In Our Daily Life?
pH scale is a scale for measuring hydrogen ions concentration. pH range between 0 to 14 thus, pH is a number which indicate the acidic or basic nature of a solution. The neutral value of pH is 7. A value less than 7 represent an acidic solution, while a value of more than 7 represent the basic nature of the solution.
Importance of pH in our daily life:
(i) pH of soil in the backyard: Every plant requires a specific pH for healthy growth. The optimum pH required for growth of a plant can be known by finding the pH of the place where such plant grow.
(ii) pH of our digestive system: Our stomach produce HCL which helps in the digestion of food. When the stomach has produce too much acid we feel pain and irrigation which are the indication of indigestion. To face this problem we take antacid which neutralize excess acid and bring relief.
(iii) pH changes as cause of tooth decay: Tooth enamel is calcium phosphate and is the hardest substance in the body. It does not dissolve with water buts gets corrode at pH below 5.5. Bacteria present in the mouth produce acid by dehydration of food particle left in the mouth after eating and thus spoil the teeth.
(iv) Plants and animal are pH sensitive: Living organism can survive in the narrow range (7.0 to 7.8) of pH. When acid rain flows into the river its lower the pH value and make survival of aquatic life difficult.
┬а
┬а
┬а
The Common Salt
(i) Chemical name: Sodium Chloride
(ii) Common name: Common salt
(iii) Other name: Rock salt, Ocean salt, Table salt, King of salt.
(iv) Chemical formula: Nacl
(v) Formation: NaOH + HCL тЖТ NaCl + H2O
(vi) Uses: It is used in formation of many of the salt. It is essential part of our diet. It is used in preservative for a number of food material like packed meat, pickle etc. It is used an anti-freezing agent. It is used in industries like soap, packed food, etc.
┬а
What Is The Use Of Base? Explain With Example.
Different of bases are:
(i) Sodium Hydroxide: Its commercial name is caustic soda and its chemical formula is NaOH. It is used in manufacturing of soap, for making artificial fiber like rayon and in paper industries.
(ii) Potassium Hydroxide: Its commercial name is caustic soda and its chemical formula is KOH. It is used in manufacturing of nickel iron storage battery or absorbing CO2 and in soap industries.
(iii) Calcium Hydroxide: Its commercial name is slaked lime and its chemical formula is Ca(OH)2. It is used in manufacturing of bleaching powder in white washing and testing of carbon dioxide gas.
(iv) Magnesium Hydroxide: Its commercial name is milk of lime and its chemical formula is Mg(OH)2. It is used in manufacturing of antacid or neutralization of acid in the stomach for removing Greece from cloth in dry cleaning and in cleaning window pans.
(v) Ammonium Hydroxide: Its commercial name is Ammonia water and its chemical name is NH4OH. It is used in as a cleaning agent and sanitizer in many household and industry cleaner.
┬а
What Do You Understand By The Family Of Salt?
Salt are the ionic compound consisting of two parts one part carrying a positive charge cation and the negative charge anion.
┬а
What Is The Process Of Brine Preparation?
It is aqueous mixture of sodium chloride and water. When we pass electricity through this solution then it produces NaOH + H2O тЖТ NaOH + H2 + Cl. This process is known as Chloro alkali process.
┬а
What Are The Properties Of Common Salt?
Colour and taste: It is a colour less mixture with melting point 820 oC
Solubility: It is soluble at room temperature.
Action of heat: At room temperature it exists in the form of dehydrate sodium chloride. When we heat these crystals then the water molecules come out in the form of water and a black residue of NaCl remain.
Hygroscopic Nature: It is hygroscopic in nature because it absorbs moisture from the surrounding.
Action with Concentrated Sulphuric Acid:
H2SO4 + NaCl тЖТ NaHSO4 + HCl
Action with silver nitrate:
AgNo3 + NaCl тЖТ NaNo3 + AgCl
┬а
The Bleaching Powder
(i) Chemical Name: Calcium Oxychloride
(ii) Chemical formula: CaOCl2
(iii) Formation: Ca(OH)2 + Cl2 тЖТ CaOCl2 + H2O
(iv) Colour or state: It is yellowish white powder
(v) Action with air: CaOCl2 + CO2 тЖТ CaCo3 + Cl2
(vi) Solubility in water: It is soluble in cold water. It makes the water milky because bleaching powder contain some un react lime which are insoluble in water and makes the water milky.
(vii) Uses:
Textile industry for bleaching cotton and linen.
It is used in Laundry for beaching washed clothes.
It is used in wool making industries.
Discuss About The Baking Soda?
(i)Chemical Name: Sodium: Bi carbonate
(ii) Chemical Formula: NaHCO3
(iii) Formation: NaCl + CO2 + H2O тЖТ NH4Cl + NaHCO3
(iv) Colour and state: It is a white crystalline solid.
(v) Action of air: It is stable in air.
(vi) Solubility in water: It is soluble in water the solution will be alkali.
NOTE: We use baking soda in bakery or in kitchen because when we add baking soda in any substance it makes the food fluffy. Their carbon dioxide is responsible for the fluffiness of food like in cake. In bakery Baking powder is used instead of baking soda because baking powder contain mild acid like tartaric acid.
(vii) Uses of Baking soda: It is used in kitchen.
It is also used in medicine as antacid.
It is used in soda acid fire extinguisher.
┬а
How Are Bases Different From Alkalis?
Base which are soluble in water and produce OH- are called alkalis. Some examples are:
Sodium hydroxide NaOH тЖТ Na+ + OH-.
Potassium hydroxide KOH тЖТ K+ +OH-.
All alkalis are base but all base are not alkalis. For examples A(OH)3 is a base but not a alkalis.
┬а
When Zinc Metal Is Treated With A Dilute Solution Of A Strong Acid, A Gas Is Evolved, Which Is Used In The Hydrogenation Of Oils Name The Gas Evolved. Write The Chemical Equation Of The Reaction Involved And Also Write A Test To Detect The Gas Formed?
The gas evolved is hydrogen gas which is used in the hydrogenation to produce Vanaspati. The equation of the reaction is: Zn+2HCL тЖТ ZnCL2+H2.
Hydrogen gas burs with pop sound 2H2+O2 тЖТ 2H2O.
┬а
Name The Acids Which Are Present In The Following Stuff Which Attribute A Sour Taste To Them: Lemon Juice, Vinegar, Vitamin C Tablet, Tamarind, Sour Milk, Orange
Lemon juice contain citric acid.
Vinegar contain acetic acid.
Vitamin C tablets contain ascorbic acid.
Tamarind contains tartaric acid.
Sour milk contains lactic acid.
Orange contains citric acid.
┬а
The Washing Soda
(i) Chemical Name: Sodium Carbonate Deca Hydrated
(ii) Common Name: Washing Soda
(iii) Chemical formula: Na2Co3.10H2O
(iv) Preparation: NaCl + Co2 + H2O + NH3 тЖТ NH4Cl + NaHCO3
(v) Colour and state: It is transparent crystalline solid containing 10 molecules of water of crystalline
(vi) Action in air: Na2CO3.10H2O тЖТ Na2Co3H2O + 9H2O
(vii) Solubility in Water: It dissolve in water and form solution which is slightly alkali in nature.
(viii) Action with acid: Na2Co3 + HCL тЖТ NaCl + H2O + CO2
(ix) Uses of washing Soda: Washing soda is used for cleaning purpose.
It is used to remove the permanent hardness of water.
It is used in the manufacturing the manufacturing of number of useful Product like glass, soap, paper caustic soda etc. It is used in laboratory agent for example Its standard can be prepare to Carry out acid base titration.
┬а
What Type Of Precaution Are Used While Handling Acids In The Laboratory?
All living things are very sensitive to acids and too much acid can kill cells or stop proper working of cells. Concentrated acid are very dangerous and should never be handled without protection.
The following projection must be observed while dealing with acids.
(i) Never try to touch or taste acid which are used in the laboratory.
(ii) Never add water into concentrated acid otherwise bottle will break. Always add conc. Acid to water very slowly with continuous cooling under running water.
┬а
What Are The Advantages Of Acids?
(i) Hydrochloric acid is released in stomach to make medium acidic in nature. It leads to coagulation of protein and helps in their digestion.
(ii) HCL kills bacteria coming to stomach along with the food.
(iii) Vinegar (Acetic acid) is used as preservation in pickles and in chines food. It gives sour taste to the food.
(iv) Cold drinks contain carbonic acid.
(v) Lemon contain citric acid which is used in case of indigestion.
(vi) Orange and Amla contain ascorbic acids (Vitamin C) while prevent scurvy.
Q30 What do you understand by the Strong and Weak acids?
Ans. Strong Acid: Those acids which dissociate into ions completely is called Strong acids. For example H2SO4, HCL, HBr, HI, HNO3, HCIO4 are strong acids.
Weak acids: Those acids which do not dissociate into ions completely are called weak acids. For example: Citric acid, Acetic acid, Ascorbic acid, Tartaric acid, Formic acid.
┬а
Why Do We Not Categories Metal Oxides As Salts While We Categories Metal Sulphide As Salts?
Salts are formed by reaction of base with acid. Sulphide are regarded as salts because they are formed from acid (H2S) and base (like NaOH,KOH)
2NaOH + H2S тЖТ Na2S + 2H2O
┬а
The Plaster of Paris
(i) Chemical formula: CaSO4. ┬╜ H20.
(ii) Chemical name: Calcium sulphate hemi hydrated.
(iii) Formation: CaSO4.2H2O тЖТ CaSO4.┬╜ + 1┬╜ H2O.
(iv) Action of water: CaSO4. ┬╜ H2O тЖТ CaSO4.2H2O.
(v) State and colour: It is white powder form.
(vi) Uses: It is used to make design on wall and ceiling.
It is also used in making toy, statue, decorate material
It makes the surface smooth like surface of wall before painting.
It is also used in make of chalk.
In medical science it is used for setting fracture bones in the right position.
┬а
┬а