Class 10 Science Chapter 4 Important Questions
Class 10 Science Chapter 4 Important Questions of Carbon and its Compounds are given below. All the questions are taken from NCERT Textbook and confined to CBSE Curriculum 2020-21, which are important for CBSE Exams 2020-2021.CBSE Board Questions are given on separate page. These questions provide the complete revision of Chapter 4 Class 10 Science. We have tried to include all the possible questions from the textbooks.
Class 10 Science Chapter 4 Important Questions 2020-21
|Chapter 4:||Important Questions for 2020-21|
Class 10 Science Chapter 4 Important Extra Questions
Class 10 Science Chapter 4 Important Questions are given below updated for new academic session 2020-21. There are questions covering the entire chapter 4 of class 10 Science. It includes the intext questions answers and some extra questions based on activities and exercises.
10th Science Chapter 4 Important Questions Set – 1
What are the product which based on the Versatile of Carbon compound?
Food, clothes, medicines, books, or many of the things that you listed are all based on this versatile element carbon. In addition, all living structures are carbon based. The amount of carbon present in the earth’s crust and in the atmosphere is quite meagre. The earth’s crust has only0.02% carbon in the form of minerals (like carbonates, hydrogen- carbonates, coal and petroleum) and the atmosphere has 0.03% of carbon dioxide. In spite of this small amount of carbon available in nature, the importance of carbon seems to be immense.
Explain the formation of Covalent compound: (i) Chlorine molecules (ii) Carbon tetra chloride (iii) Ammonia.
(i) Formation of chlorine molecules: Two chlorine atom shares one electron of each and acquire stable electronic configuration.
(ii) Formation of carbon tetrachloride: Carbon atom has four electrons in the outermost shell. In the formation of carbon tetrachloride, it shares four electrons with four chlorine atoms. In turn four chlorine atoms shares one electron each with one carbon atom. Thus in all one carbon atom and four chorine atom complete their octet by mutual sharing of electrons and carbon tetrachloride containing four covalent bond is formed.
(iii) Formation of ammonia molecules: Nitrogen(N) atom has 5 electrons (2, 5) in the outermost shell. It shares one electron each of three hydrogen atom to form ammonia molecules. One unshared paired of electron in ammonia molecule is not involved in bond formation and is called a lone pair of electrons.
What is meant by double bond or double covalent bond? Give examples.
The bond between two atoms formed by sharing of two pairs of electrons is called a double bond. Two horizontal lines between two atoms denote a double bond example O≡O
(i) Formation of Oxygen atom has six electrons in its outermost shell, two short of forming a complete octet. Thus each oxygen atom in O2 shares 2 electrons with the other oxygen atom attain stable configuration.
(ii) Formation of ethylene molecule (C2H4): In ethylene two carbon atom shares two pair of electron between them and the rest two electrons on each carbon atom share one electron each with two hydrogen atoms. Thus ethylene molecules has one double bond(C=C) and four single bonds (C-H)
What is triple bond or triple covalent bond? Explain the formation of triple bond giving two examples.
The bond formed between two atoms through the sharing of three electron pairs is called a triple bond. Three horizontal lines between two atoms denote a triple bond example nitrogen molecule is given as N≡N.
(i) Formation of N2 molecules: Nitrogen atoms have five electrons in their outermost shells. Therefore, in N2 molecules two nitrogen atom shares 3 electrons with each other, Thus acquiring the stable structure and forming a N2 molecule with triple bond.
(ii) Formation of acetylene molecule(C2H2): In acetylene molecule, each carbon atom satisfies its valency by sharing one electron with a hydrogen atom and sharing the other three electrons with the other carbon atom.
The covalent compound is said to be formed when two atoms achieve stability by the sharing of electron pair, each contributing one electron to the electron pair. In this way the atom can be regarded as having acquired a noble gas configuration.
10th Science Chapter 4 Important Questions Set – 2
What are the physical properties of carbon compound or covalent compounds?
Covalent compound exhibit the following properties:
(i) These have low melting and boiling point.
(ii) These do not conduct electricity either in the solid state or in the molten state or in the solution form. They are non-electrolyte.
(iii) These are readily soluble in non-polar solvent like benzene, carbon tetrachloride etc., but do not dissolve in polar solvent like water.
(iv) The covalent bond is directional in nature.
Why are covalent compound generally low melting point?
Covalent compounds have strong bonds within the molecule and intermolecular force are very weak and so have low melting and boiling points.
Why are covalent compounds poor conductor of electricity?
Covalent compound are formed due to sharing of electron between atoms and no charged particle are formed, hence such compound is generally bad conductor of electricity.
Why are some elements in molecular form while other are in atomic form?
Elements of stable configuration exist in atomic form. For example, inert gases He, Ne, Ar, etc. Elements which are short of inert configuration by 1,2 or 3 electron shell (contain 5, 6, 7 electrons) achieve stable configuration by sharing requisite number of electron with other atoms and exist in molecular form. For example, chlorine atom has 7 electrons in their outermost shell, thus two Cl atoms share one electron of each other and exist as Cl-Cl (Cl2).
Allotropy in Nature
When an element possesses two or more different crystalline forms in the same state they are called allotropes and the phenomenon is known as allotropy. Diamond and graphite are the two allotropes of carbon. They are chemically identical when equal quantities of diamond and graphite are burnt both of these produce the same amount of carbon dioxide. However, as they exist in different form in the solid state, they have entirely different physical properties.
10th Science Chapter 4 Important Questions Set – 3
Why do carbon form largest numbers of compounds? Give two reasons.
Carbon has two unique features:
(i) It is tetravalent.
(ii) It has the property of catenation.
The above two feature enables carbon to form a large numbers of compounds with varying size, shape that’s why carbon atom has long chain or even are arranged in branches or rings. Because of tetra-valency carbon atom in its compound are linked by single, double or triple bonds. Carbon atom are also bonded with oxygen, hydrogen, chlorine, nitrogen and sulphur giving rise to compounds with specific properties typical of the element other than carbon present in the molecule.
Differentiate between saturated and unsaturated hydrocarbon giving one example each.
A hydrocarbon in which each carbon atom is attached to four other atoms is known as saturated hydrocarbon. The bonds so formed are single covalent bonds. These hydrocarbons are also called alkanes.
Hydrogens containing either a carbon double bond (C=C) or a carbon-carbon triple bond in their molecules are called unsaturated hydrocarbon.
Why does only carbon exhibit property of catenation and form large number of compounds with other elements?
Carbon atom has a small size and this enables its nucleus to hold on the shared pair of electron quite strongly. This is why carbon forms strong bond with most other elements and the compounds formed are exceptionally stable as compared to covalent bond formed by other elements.
Write the name of the saturated hydrocarbon having two carbon atom. Also write its chemical formula.
Saturated hydrocarbon having to carbon atom is ethane. Its chemical formula is C2H6.
Catenation Property of Carbon
The unique property of carbon to form bonds with other carbon atom giving rise to large molecules is called catenation. Due to catenation compounds of carbon have long chain of carbon and even carbon atoms arranged in rings.
10th Science Chapter 4 Important Questions Set – 4
(a) What are hydrocarbons? Give one example. (b) Mention the structural difference between saturated and unsaturated hydrocarbons. Write two example each.
(a) Compound containing carbon and hydrogen are called hydrocarbon example methane (CH4).
(b) Structural difference- Saturated hydrocarbon have all its carbon connected to each other by only single bond whereas in unsaturated hydrocarbons there are one or more double or triple bonds between two carbon atoms.
Saturated hydrocarbon- methane (CH4), ethane (C2H6).
Unsaturated hydrocarbon- ethane (C2H4), ethyne (C2H2).
How are hydrocarbons classified?
Hydrocarbon can be classified either on the basis of nature of bonds or nature of chains between carbon atoms.
(a) On the basis of bonds, hydrocarbons are classified as
(i) Saturated hydrocarbon. Example CH4 (methane).
(ii) Unsaturated hydrocarbon. Example C2H4 (ethene).
(b) On the basis of chains, hydrocarbons are classified as
(i) Aliphatic hydrocarbon: They have straight or branched chain of carbon atom. Example: butane and isobutene.
(ii) Cyclic hydrocarbon: These contain rings of carbon atoms. Example: Cyclohexane and benzene.
Name any other elements which like carbon can form compounds which have chains upto seven or eight atoms. How do these compound differ from carbon compound?
Silicon forms compound which have chains like carbon. Compound formed by silicon are few and are not so reactive.
Write the name of saturated hydrocarbon having 3, 4, 5 and 6 carbon joined in a straight chain?
We first write the carbon atoms joined together in a chain and then fill the remaining valences with hydrocarbon atoms. In this way we get following structures for saturate hydrocarbon having 3,4,5 and 6 carbon atoms respectively. Then name these according to the number of carbon atoms example propane, butane, pentane and hexane for saturate hydrocarbon containing 3,4,5 and 6 carbon atoms respectively.
Propane or C3H8
Butane or C4H10
Pentane or C5H12
Hexane or C6H14
The group formed by removal of the hydrogen atom from an alkane molecule is called an alkyl radical or alkyl group. For example, if hydrogen is removed from methane, it is –CH3 (methyl) group.
10th Science Chapter 4 Important Questions Set – 5
Write the molecular formula for an (i) alkene and (ii) alkyne with four carbon atom.
The molecular formula for an alkane 4 carbon atom is C4H10. An alkene contains 2 hydrogen atom less than the corresponding alkane and an alkyne contain 4 hydrogen atom less than corresponding alkanes. Therefore, molecular formula of
(i) alkene is C4H8
(ii) alkyne is C4H6
Which of the following compounds can have a triple bond? C2H4, C3H4, C3H8.
The compound having a triple bond is called an alkyne. It has 4 hydrogen atom less than the corresponding alkane. Therefore, C3H4 is an alkyne. (Its corresponding alkane is C3H8).
What are the groups, other than hydrogen part, present in carbon compound called?
What is meant by the functional group? Give example.
A group which determines the chemical nature of an organic compound is called a functional group. For example, Cl in CH3Cl, OH in CH3OH are functional group.
A homologous series in a group or family of compounds which contain the same functional group but have different chains lengths thus these have the same chemical properties but different physical properties but different physical properties that vary in a regular manner.
Characteristics of homologous series
(i) It has a general formula in term of number of carbon atoms.
(ii) It has the functional group if any,
(iii) The member of a homologous series that’s why homologous have similar chemical properties.
(iv) Various homologous can be prepared by the general method of preparation for the series.
(v) Two successive (adjacent) homologous differ by 1 carbon atom and 2 hydrogen atoms in their molecular formulae.
(vi) The members of a homologous series show a gradual change in their physical properties with increases in molecular mass.
10th Science Chapter 4 Important Questions Set – 6
Write the general formula for alkenes and alkynes?
The general formula for alkanes CnH2n+2. Since an alkene contain two hydrogen atom less than the corresponding alkane, therefore the general formula for alkenes is CnH2n. Further since an alkyne contain 2 hydrogen atoms less than the corresponding alkene hence the general formula for alkynes is CnH2n-2.
Select hydrogen which are member of the members of the same homologous series Give also the name of each homologous series you find represented in the following: CH4, C2H2, C2H4, C2H6, C4H10, C3H4, C3H6.
(i) CH4, C2H6, C4H10 represent homologous series called alkanes.
(ii) C2H4, C3H6 represent homologous series called alkenes.
(iii) C2H2, C3H4 represent homologous series called alkyne.
What is the difference in the molecular formula of any two adjacent homologous? (i) In term of molecular mass. (ii) In term of number of and kind of atoms in their molecules.
Two successive homologous should differ:
(i) by 14 in molecular mass and
(ii) one carbon atom and two hydrogen atom in terms of atoms in their molecules.
What is Isomerism?
The phenomenon in which two or more compounds having same molecular formula may exist with different structural formulae is called isomerism.
The compound that contain the same molecular formula but different structures are called structural isomers. The isomers of a compound have same chemical properties and different physical properties.
10th Science Chapter 4 Important Questions Set – 7
Discuss about the nomenclature of hydrocarbon.
1. The number of carbon atom in a hydrocarbon (or any other organic compounds) is indicated by the following steam:
One carbon atom is indicated by writing “Meth”
Two carbon atoms is indicated by writing “Eth”
Three carbon atoms is indicated by writing “Prop”
Four carbon atoms is indicated writing “But”
Five carbon atoms is indicating by writing “Pent”
2. Straight chain hydrocarbons
(i) A straight chain saturated hydrocarbon containing single bonds is indicating by writing the word “ane” after stem. For example, a four carbon atom saturated hydrocarbon(C4H10) is called butane and a-5c atom straight saturated hydrocarbon is called pentane (C5H12).
(ii) An unsaturated hydrocarbon containing a double bond is indicating by writing the word “ene” after the stem
(iii) An unsaturated hydrocarbon containing a triple bond is indicating by “yne” after the steam.
3. Branched chain saturated hydrocarbon: The following rule should be followed for naming branched chain saturated carbon.
(i)First find out the longest chain of carbon atoms in the structure of the compound. The compound is then named on the basis of number of carbon atoms present in the longest chain. (This is called parent hydrocarbon).
(ii) The methyl groups present as side chains are considered substituents and named separately, e.g. methyl (CH3-) or ethyl (C2H5-) groups.
(iii) The carbon atoms of the parent hydrocarbon are numbered in such a way that the alkyl groups (substituents) get the lowest possible number. That is, the terminal carbon atom which is nearest to the carbon atom containing an alkyl group (or a substituent) is given number 1.
(iv) The position of the alkyl group is indicated by writing the number of carbon atom to which it is attached.
(v) The IUPAC name of the compound is obtained by writing the (position and name of alkyl group just before the name of the parent hydrocarbon.
4. Hydrocarbons containing functional groups: In case a functional group is present, it is indicated in the name of the compound with a prefix (for halides) and a suffix for other functional groups. If the name is to be given by a prefix, then halo (chloro, bromo, iodo) is written before the name of the corresponding hydrocarbon, e.g. chloropropane is CH3CH2CH2Cl. If the name of the functional group is to be given by a suffix, the name of the carbon chain is modified by deleting the final “e” and substituting the appropriate suffix. For example, a two carbon chain with an aldehyde group would be named as:
(i) Ethane – e = ethan + “al” = ethanol
(ii) A three carbon chain with a ketone group
Popane – e = propan + “one” = propanone
(iii)A three carbon chain with an alcoholic group
Propane – e = propan + “ol” = propanol
(iv) If the carbon chain is unsaturated then final “ane” is the name of carbon is substituted by “ene” or “yne”; a three carbon chain with a double or triple bond.
Propane – ane = prop + “ene” = propane (double bond)
Propane –ane = prop + “yne” = propyne (triple bond)
Give IUPAC name of the following compound: CH3-CH=CH2. What is its common name?
(i) The given compound satisfied the formula of alkenes CnH2n and has one double bond and is named as an alkene. Therefore, ending ene- is to be used.
(ii)C3H6 contains 3 carbon atoms in the main chain and the Greek word for 3 is prop. Therefore, the compound is propane.
(iii) The position of double bond is to be indicated and the carbon atom joined with a double bond should appear at the lowest possible number. When the carbon atoms are numbered from left hand side, the double bond appears between carbon 2 and 3. When the carbon atoms are numbered from the right hand side, the double bond appears between carbon atom 1 and carbon atom 2. Since we have to name it in such a way that the carbon joined by a double bond carries the lowest possible numbers. Therefore, the correct IUPAC name of this compound is 1-propane or simply propane.
Why is the concept of functional group important in inorganic chemistry?
The concept of functional group is important in organic chemistry for the following reasons:
(i) Functional groups are taken as the basis for naming of the organic compounds.
(ii) Organic compounds are classified on the basis of their functional groups.
(iii) Functional groups are the sites of chemical reactions. Compounds containing the same functional group show similar chemical behavior.
Discuss the nomenclature of alkyl halides
(i) The general formula of alkyl halides is CnH2n+1.X, where X is the halogen atom (F, Cl, Br, I).
(ii) Longest carbon chain is chosen and the alkyl halide is named by adding the prefix: Fluro (F), Chloro (Cl), Bromo (Br) and Indo (I) before the alkane of the main chain.
(iii) The position of halogen atom is indicated by a number assigned to the carbon atom to which it is attached.
(iv) The prefixes di-or tri- are used if 2 or 3 halogen atoms of the same element are attached to the amin carbon chain.
Characteristic of Isomers
(i) They have the same molecular formula.
(ii) They have different structural formula.
(iii) They have different melting and boiling point.
(iv) They have different chemical properties.
10th Science Chapter 4 Important Questions Set – 8
Give the IUPAC name of the following compounds: CH3CHBr2, BrCG2CH2Br.
(i) The functional group in CH3CHBr is bromine.
(ii) Since it has two C-atoms and 2-Br atoms, it should be named as dibromo ethane.
(iii) Both the bromine atoms are attached to the same C-atom and so the carbon chain should be numbered from the C-atom attaching bromine atoms.
Common name: Ethylidene dibromide.
IUPAC name: 1, 1 dibromo ethane.
IUPAC name of BrCH2CH2Br: 1, 2 dibromo ethane.
Identify the functional group in CH3CHO. Write its common name and IUPAC name.
(i) The functional group in CH3CHO is the aldehyde group (-CHO.
(ii) CH3CHO contains 2 atoms and is therefore, named as derivative of ethane.
(iii) Since CH3CHO is an aldehyde, the suffix –e of ethane is replaced by the suffix-al.
(iv) The IUPAC name of CH3CHO is Ethanal.
(v) The common name of CH3CHO is Acetaldehyde.
How are carboxylic acids named?
General formula of carboxylic acid is R-COOH/ They are named by replacing suffix “e” of corresponding alkane as given from the total number of carbon atoms by “oic” and then adding at the end.
Formula Common name Name (IUPAC)
HCOOH Formic acid Methanoic acid
CH3COOH Acetic acid Ethanoic acid
C2H5COOH Propionic acid Propanoic acid
Choose those compounds from the following which can turn blue litmus solution red:HCHO, CH3COOH, CH3OH, C2H5OH, HCOOH, CH3CHO. Give reasons for your choice.
HCHO, CH3COOH re aldehydes. HCOOH, CH3COOH are carboxylic acids. CH3OH and C2H5OH are alcohols. Out of these only carboxylic acids would turn blue litmus solution red. So HCOOH and Ch3COOH would turn blue litmus solution red.
The hydroxyl group (-OH) when present in aliphatic organic compounds is known as an alcoholic group. The corresponding compound is an alcohol. An alcohol is named in IUPAC system by replacing –e of the corresponding alkane by the suffix –ol.
10th Science Chapter 4 Important Questions Set – 9
Write the next homologue of propanol (CH3CH2CH2OH) and butanal (CH3CH2CH2CH0).
Next homologue of propanol-butanol (CH3CH2CH2CH2OH).
Next homologue of butanal-pentanal (CH3CH2CH2CH2CHO).
What should be maximum number of carbon atoms in a molecule of alkane to exhibit phenomenon of isomerism?
The general formulae of a homologous series of carbon compounds is cnH2n+1OH. Write the molecular formulae of the fourth and fifth members of the series.
Giving example, explain why some substances (i) burn without a flame (ii) burn with a flame (iii) burn with a flame and soot is formed.
(i) Wood, charcoal when ignited burn with a flame in the beginning due to vapourisation of volatile substances and then these just glows red and gives out heat without a flame.
(ii) Candle, LPG gas stove burns with a flame. This is because in these cases gaseous substance burn.
(iii) If there is insufficient oxygen/air soot is produced.
Carboxylic acids containing long chain of carbon atoms are fatty acids. They are use as mild acids in foods, cold drinks, drugs, perfumes and are chief constituents of washing soaps.
10th Science Chapter 4 Important Questions Set – 10
How do you differentiate saturated and unsaturated hydrocarbons with the help of combustion reactions?
(i) Saturated hydrocarbons burn with a blue flame.
(ii) Unsaturated hydrocarbons will give a yellow flame lots of black smoke.
Explain why (i)In wood fired chulhas gaps are left between the logs. (ii)Grate is made in a coal or charcoal sigree or angithee. (iii) A perfaround sheet is kept around the wicks in a wicks stove.
In all the above cases provision are made for the adequate supply of supporter substance, air (oxygen) that’s why
(i)In wood fired chullhas gaps are left between the logs so air can enter the burning site and can provide oxygen for the combustion of logs.
(ii) Grate is made in a coal or charcoal sigree or antigrithee so that supply of air(oxygen) will be adequate for the combustion of coal or charcoal.
(iii) A performed sheet is kept around the wicks so that air can reach the wicks easily through perforations or holes and supply of oxygen remains adequate for the combustion of kerosene.
What is the difference between combustion and oxidation? Give two oxidation reaction of carbon compounds.
Combustion is the burning of compounds in air to give CO2 and water with the liberation of heat and light.
Oxidation is the reaction in which carbon compounds take up oxygen in the presence of oxidising agents to give another carbon compound. Thus all combustion reactions are also oxidation reaction but oxidation are not combustion reactions. In fact combustion means complete combustion.
(i) Carbon compound on combustion(complete oxidation) CO2 and H2O
CH4 + 2O2 → CO2 +2H2O
(ii) Alcohols are oxidised to acid in the presence of alkaline potassium permanganate or acidified potassium dichromate.
CH3CH2OH → CH3COOH
(iii) With cold dilute alkaline potassium permanganate, ethene(ethylene) is oxidised to ethylene glycol.
CH2 = CH2 → CH2OH
List any two difference between saturated and unsaturated carbon compounds?
In an addition reaction an atom or group of atoms are added to an unsaturated compound while in substitution reaction an atom or a group present in saturated compound is replaced by another atom or group without the compound undergoing any change in its burn with yellow or sooty flame.
(i) (a) Addition of chlorine by ethylene
CH2 = CH2 + Cl2 → CH2Cl-CH2Cl
(b) Unsaturated hydrocarbon add up hydrocarbon in the presence of catalyst such as palladium or nickel to give saturated hydrocarbon.
CH2 = CH2 → CH3 – CH3
(ii) Substitution of chlorine for hydrogen in ethane.
C2H6 + Cl2 → C2H5Cl + HCl
The addition of molecules of the same kind to form a long chain molecule is known as polymerisation. For example, when ethylene is heated to high temperature under high pressure in the presence of catalyst (conc. H2SO4) it polymerises to polyethylene.
nCH2 = CH2→ – CH2 – CH2 – CH2 – CH2 – CH2–
10th Science Chapter 4 Important Questions Set – 11
State physical properties of alcohols.
Physical properties of alcohols are:
(i) State: Most common alcohols are liquid.
(ii) Electrical conductivity: Like hydrocarbon they do not conduct electricity.
(iii) Solubility: Lower member of the series example methanol, ethanol, propanol are quite soluble in water. As the number of carbon increases the solubility readily decreases.
(iv) Action on sodium: They react with sodium produce hydrogen.
(v) Action of heat: They readily burns like hydrocarbons.
(vi) Boiling point: Boiling point of alcohol are higher than the hydrocarbon of the same molecular weight.
What are the uses of ethyle alcohol?
(i) It is a very important solvent for many organic compounds.
(ii) It is used to sterilise wounds and syringes.
(iii) It is used as solvent for laquers, varnishes, perfumes, medicine etc.
(iv) It is used in the manufacture of paints, dyes, medicines and a large number of organic compounds.
(v) It is used for making antifreeze mixture which are used in the radiators of motor vehicle in cold countries because water with ethyl alcohol has a much lower freezing point than water itself.
(vi) It is used for alcoholic drink like whisky, wine, beer other liquors.
(vii) It is also used as a fuel.
What is fermentation? Give two examples of fermentation?
Fermentation: It is a slow process of breaking down of organic compounds by microorganism to simpler molecules. It is an exothermic process and is carried out at 20-30 degree Celsius.
(i) Production of ethyl alcohol from molasses (cane sugar)
C12H22O11 + H2O → 4C2H5OH + 4CO2.
(ii) Production of acetic acid from fermented liquors (15% ethyl alcohol)
CH3CH2OH → CH3COOH
What is molasses? Give its uses.
After the crystallization of cane sugar from syrup of sugarcanes, the solution still contains 60-70% solute comprising mainly of cane sugar fructose and glucose. This solution is known as molasses and is used from the production of alcohol.
Enzymes are catalyst which bring about biochemical changes. For example, lactose enzymes turn milk sugar, lactose into lactic acid.
10th Science Chapter 4 Important Questions Set – 12
Briefly describe the effect of harmful effect of alcoholic drinks on human body. How can they be disastrous to the family as well as to the person himself?
Harmful effects of alcohol on human being:
(i) It is an intoxicant. Under the influence a person loss mental balance to distinguish between right and wrong.
(ii) Excessive of alcoholism affects the lungs of a person and may lead to his death.
(iii) It make the person to addicted to its uses.
(iv) Its consumption causes continuous economic loss to the family.
(v) If a person take alcohol adulterated with methanol or pyridine he is liable to lose his eye sight.
What happen when sodium reacts with ethyl alcohol?
When a piece of sodium metal is poured over ethyl alcohol, vigorous reaction occurs and hydrogen gas is bubbled out.
2C2H5OH + 2Na → 2C2H5ONa + H2
What is Esterification?
The reaction in which an alcohol combine with a carboxylic acid in the conc. sulphuric acids is called Esterification.
What is a mixture of water and alcohol used instead of water in radiators of vehicle in cold countries?
Water freeze at 0 degree Celsius. Thus in cold countries where the temperature falls below 0 degree Celsius, water cannot be used in radiators. Therefore, a mixture of water and alcohol is used because (i) water and alcohol are miscible in all proportions and (ii) a mixture of water and alcohol has much lower freezing point than that of water.
Yeast in Fermentation
Yeast are vegetable organism present in the yeast plant. They contain the enzyme zymase and invertase. Invertase converts unfermentable sugar to fermentable sugar that’s why fructose and glucose. Zymase ferments sugars to alcohol and carbon dioxide.
10th Science Chapter 4 Important Questions Set – 13
How would you test for an alcohol?
(i) To 1 cc of the given compound add 0.5 g sodium acetate and a few drops of concentrated sulphuric acid, pleasant fruit smell of an esters shows the presence of –OH, the hydroxyl group or alcoholic group in the compound.
(ii) To 2-3 cc of the compound add a few pieces of anhydrated CaCl2. Keep it for a few minutes and then filter in a dry test tube. To the filtrate add a small piece of sodium metal. Evolution of hydrogen gas with brisk effervescence indicates the presence of an alcoholic group in the compound.
What do you understand by the followings terms? (i) Reactified spirit (ii) Methylated spirit (iii) Absolute alcohol.
(i) Reactified spirit: It is ethyl alcohol containing 4.4% water.
(ii) Methylated spirit: It is reactified spirit to which 5-10% of poisonous substance such as methanol, pyridine or mineral naptha has been added to prevent its misuse for drinking.
(iii) Absolute alcohol: It is 100% ethyl alcohol totally free form of water or any other impurities.
What are the uses of Ethanoic acid?
Uses of Acetic acid or ethanoic acid are as follows:
(i) It is used as vinegar for preparing pickles.
(ii) It is used for the preparation of aspirin used for relieving headache.
(iii) It is used for preparing cellulose acetate which is an important artificial fibre.
(iv) It is used to coagulate rubber from latex.
What are esters? Write a chemical reaction to illustrate it.
Esters are the sweet smelling substances. These are used in making perfumes and flavouring agents. Esters are obtained when an alcoholic is warmed with a carboxylic acid in the presence of conc. sulphuric acid.
CH3COOH + C2H5OH → CH3COOC2H5 + H2O
Esters react with acids or bases to give back the alcohol and the carboxylic acid example:
CH2COOC2H5 + NaOH/HCl → CH3COOH + C2H5OH
Ethyl alcohol is a part of drinking beverages. It is also used widely as a solvent in industries. To make it unsuitable for drinking certain poisonous substance like pyridine methyl alcohol and copper sulphate are added to it. This is called denatured alcohol. Methylated spirit is ethyl alcohol to which some methyl alcohol is has been added to make it undrinkable.
10th Science Chapter 4 Important Questions Set – 14
The reaction of an esters to react with an acid or base to give back the alcohol and carboxylic acid is called Saponification. This is so called because this reaction is used in the preparation of soap.
Why do soaps not work in hard water?
When soap is added to a sample of hard water, calcium and/or magnesium ions present in hard water react with soap forming insoluble calcium/magnesium soap which is sticky and greasy mass and thus no lather is formed.
Ca2+ + 2C17H35COONa → (C17H35COO)2Ca + 2Na+
What is a micelle? Explain the mechanism of cleaning action of soap?
Soap or detergent consist of two part with distinct properties. One part or end consist of a large hydrocarbon tail which is hydrophobic. When a soap is added to the water it does not form a true solution but is dispersed in a way that the ionic end is in water and the hydrophobic part produce out of water. Inside water this given rise to the formation of clusters or molecules in which the hydrophobic tails are in the interior of the cluster and the ionic ends are on the surface of the cluster. This formation with a hundred or soap molecules is called a micelle.
Soap in the form of micelles is able to clean oil and dirt since it will be collected in the center of the micelle. When water is agitated the micelle with the oily dirt tend to lift off from the dirty surface and splits into fragments. This give opportunity to other tail to stick to oil if left. The negatively charged head present in water prevent the small globules so formed forming aggregates /precipitate because of ions repulsion. Thus dirt suspended in micelles is easily rinsed away.
Explain why it is difficult to wash clothes with soap when water is hard? How do detergent help in overcoming the problem?
The structure of synthetic detergent is similar to that of soaps. They have a long hydrocarbon chain which is water repelling and a short ionic part which is water attracting. The water attracting group in a synthetic detergent usually a sodium sulphonate group (SO3-Na+) or sodium sulphate group(SO4-Na+) The cleaning action of soap and detergent are similar. Thus chemically these they are not different. Difference lies only in the hydrocarbon part. Synthetic detergent made from long chain hydrocarbon obtained from petroleum whereas hydrocarbon part of soap or vegetable oils.
In soaps water attracting part is –COONa whereas in detergent it is –SO3Na.
Detergent is being preferred to soap because these form lather even with hard water and have better cleaning action.
What are synthetic detergent? Give one example of synthetic detergent. Write its advantage over soap?
Detergents are the sodium salt of a long chain benzene sulphonic acids or a longer chain alkyl hydrogen sulphate. Most of the detergent have C8 to C12 hydrocarbon chain (a non-popular group) and a polar group SO3-Na+. For example, sodium n-dodecyl benzene sulphonate and sodium n-dodecyl sulphate (or sodium lauryl sulphate).
Advantages of detergents: Ordinary washing soap (natural detergent) does not form lather in hard water or water containing Ca++ or Mg++ ions washing of clothes became difficult.
Synthetic detergents form lather even with hard water and wash clothes well.
Give two points of the difference between soaps and detergents?
1. When used with hard water a lot of it is wasted in removing Ca2+/Mg2+ salts as curdy precipitate.
2. It is completely oxidised by bacteria present in sewage and so it does not create any pollution problem in river.
1. It forms good lather with hard water and thus can be safely used even with hard water.
2. Its excess creates pollution problem in river since it is not fully biodegradable.
The Advantages and Disadvantages of Synthetic Detergents
Advantages of synthetic detergents:
(i) Uses of vegetable oils is minimized.
(ii) They can be used even with hard water.
(iii) They have better cleaning properties.
Disadvantages of synthetic detergents:
Use of synthetic detergent create water pollution because they are not easily biodegradable that’s why decomposed by microorganism.
The Cleaning Action of Soaps
Dirt is generally absorbed in the clothes as an oily material. It cannot be removed with water because it does not mix well with water. But when a cloth with dirt is soaked in soap solution the dirt and grease attach themselves to the hydrogen component (example, C15H31) of the soap molecules. The –COONa part of the soap which is attached to the water molecules pulls the hydrocarbon part along with dirt away from the surface of cloth thus washing it clean.