X Science Guess Paper Carbon and its compounds

Guess Paper  Class – X Subject - Science Carbon and its compounds

Section A – one mark each

1..Alcohols can be produced by the hydration of.

2. Write the name of C60 molecule.

3. The property of carbon to form a long chain in compounds is called ……………

4   Which of the following compounds have triple bond     C₂H₄, C₃H₄ and C₃H₆

5.    The general formula CnH2n for cyclo alkanes is the same as that of ………….

6. Write structure formula of 2- methyl propane.

7. The IUPAC name of acetylene is …………………

8. Name the functional groups present in the following compounds

CH₃COOH, CH₃COCH₂CH₃  

9.    ------and  ------are molecular formula of ethanol and propane.

10.  The IUPAC name of CH3CHO is ---------------

Section B – 2 marks each

11. Write the chemical equation of the reaction which takes place during burning of ethanol in air.

12. The molecular formula present in ester C₃H₇COOC₂H₅. Write the molecular formula of the alcohol and the acid from which it might be prepared.

13. A mixture of ethyne and oxygen is used for welding. Can you justify why a mixture of ethyne and air is not-used?

14. Write the reaction which is used as a test for ethanol and dehydration of ethanol.

15. What is reaction with ethanoic acid with ethanol?

                                             Section C – 3 marks each 

16.Write any three physical and chemical properties of ethanoic acid.

17. Write any three tests of carboxylic acids.

18. How many structural isomers are possible for pentane? Draw the structural formulae of all the possible isomers of pentane.

19. What are enzymes? Name the enzymes required for the fermentation of sugar cane to ethanol?

20. The formula of an ester is C3H7COOC2H5 write the formulae of the acid and alcohol from which the ester is prepared. 

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Q.1 Why is carbon tetravalent ?

Ans 1:Carbon atom has 4 electrons in the outermost shell.It needs 4 more electrons to complete its octet. Therefore , carbon is tetravalent .

Q.2 The formula of a hydrocarbon is Cn H2n. Name the family to which it belongs and also predict its nature.

Ans 2: The hydrocarbon belongs to alkenes It is unsaturated in nature .

Q.3 What is the valency of carbon in CH3-CH3, CH2=CH2 and HC=CH ?

Ans 3: The valency of carbon in all its compounds whether saturated or unsaturated is 4.

Q.4 Out of butter and ground nut oil , which is unsaturated in Nature?

Ans 4: Groundnut oil is unsaturated in nature .

Q.5 Why is high temperature not favourable for alcoholic fermentation?

Ans 5: The high temperature destroys the enzymes which are needed to carry fermentation .

Q.6 Name a cyclic unsaturated hydrocarbon, containing three double bonds?

Ans 6: Benzene

Q.7 What is the difference in the molecular mass of any two adjacent homologues?

Ans 7 : 14 mass units.

Q.8 Which has triple bond ; C2H4 ,C3H6 and C3H4 ?

Ans 8:C3H4 has triple bond in the formula .

Q.9 Which substance is added to denature ethyl alcohol?

Ans 9: A small amount of methyl alcohol , pyridine or copper sulphate is added to denature ethyl alcohol .

Q.10 Which ions are responsible for making water hard ?

Ans 10: Ca2+ and Mg2+ ions are responsible for making water hard.

Q.11 Name the catalyst commonly used in hydrogenation of oil to form fats?

Ans 11:Nickel.

Q.12 Write the name and molecular formula of alcohol derived from butane ?

Ans 12: C4H9OH Butanol

Q.13 Which gas is evolved when sodium carbonate or bicarbonate is added to ethanoic acid ?

Ans 13 : CO2 (carbon dioxide).

Q.14 What is SCUM ?

Ans 14: Scum is precipitate of Calcium and Magnesium salt of organic fatty acids.

Q.15 What are hydrophobic and hydrophilic parts in soaps?

Ans 15: The alkyl group(R) consisting of long chain of carbon atom is hydrophobic part while COONa group is hydrophilic in nature 

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CBSE Board guess Questions class 10 Chapter 04 Carbon and its Compounds

An organic acid ‘X’ is a liquid which often freezes during winter time in cold countries, has the molecular formula, C2H4O2. On warming   it with ethanol in the presence of a few drops of concentrated  sulphuric acid, a compound ‘Y’ with a sweet smell is formed  (i) Identify ‘X’ and ‘Y’. (ii) Write a chemical equation for the reaction involved. (i) The organic acid X is ethanoic acid (CH3COOH) and The compound Y is ethyl Ethanoate CH3 – COOH + CH3 – CH2OH ---------->  (CH3  –  C – O – CH2 – CH3 ) II O Write name of the following – i. Alkaline earth metal belonging to the third period ii. The alkali metal atom having largest atomic radius iii. The halogen atom belonging to fourth period iv. The element having lowest ionization energy v. The element having second lowest electronegativity    i.  Magnesium   ii.  Francium  iii.  Bromine  iv.  Cesium 375.6 kJ per mole    v.  Francium 380 kJ per mole Organic compound 'x' of molecular formula C2H4O2 gives brisk effervescence with sodium bi carbonate . give name and molecular formula of x with balanced equation The compound X is ethanoic acid, commonly known as acetic acid. On reaction with sodium bicarbonate, it forms sodium acetate, water and carbon dioxide gas. Thus the brisk effervescence observed is due to carbon dioxide gas. Its molecular formula is C2H4O2 . Following is the chemical equation for the reaction CH3COOH + NaHCO3 → CH3COONa + H2O + CO2 What is Saponification Reaction? Esters react in the presence of an acid or a base to give back alcohol and carboxylic acid. This reaction is used in the manufacture of soaps and is known as saponification. Soap, is nothing but the sodium salt of the carboxylate. CH3COOC2H5 ---(NaOH)--> CH3COOH + C2H5OH Ester  (ethyl ethanoate) --Base (sodium hydroxide)--> Carboxylic Acid (ethanoic acid) + Alcohol (ethanol) CH3COOH + NaOH -----> CH3COONa + H2O Carboxylic Acid (Ethanoic Acid) + Base (Sodium Hydroxide) -----> Soap (Sodium Ethanoate / acetate) + Water  Soaps are not considered as effective cleansing agent. Why? Soaps are not considered as effective cleansing agent because it is glyceride salt of soft metal like sodium which works in neutral and alkaline medium but in acidic medium get neutralized to form scum or ppt. How does melting and boiling points of hydrocarbon change with the increase in molecular mass ? With increase in molar mass, the melting point and boiling points of hydrocarbons increases generally. It is because, with increase in molar mass, the molecule becomes larger and so the van der waal's forces and other binding forces between those molecules become stronger, which holds the particles very firmly together in solid or liquid phase and so it requires more energy to break these bonds and thus the melting and boiling points of the hydrocarbons increases. Write down the relevant chemical equation involved in decolourisation. Ethene is an unsaturated compound.it has one double bond.When Bromine water(brown in colour) is added to ethene it reacts with ethene to form a new compound 1,2 dibromoethane which is colourless. The colour of bromine water is gone now. Generally bromine water is decolourise by all the compounds that contain double or triple bond. Ethane is a saturated compound with no multiple bond hence does not decolourise Br water CH2 = CH2     + Br2                 ----------> Br-CH2 - CH2- Br    A compound X has molecular formula C3H4 one mole of X reacts with 2 moles of hydrogen to yield a compound Y deduce the structure of X and Y. The molecular formula suggests that the molecule is an alkyne, as the general formula for alkyne is CnH2n-2.  So, X is propyne.  Addition of two moles of hydrogen will form the corresponding alkane, propane (C3H6).  So, X is propyne and Y is propane. HC º C - CH3 + 2 H2 --------------> CH3  -  C H2- CH3   What is dehydration reaction? Give one example. The removal of water molecule from a compound is known as dehydration. Example: Dehydration of alcohols gives alkenes. R-CH2-CHOH-R ------------->  R-CH=CH-R + H2O What is hydrolysis? Hydrolysis means addition of water to a molecule resulting in breaking of bonds that are present in the molecule. In scientific language;- Hydrolysis is a type of decomposition reaction where one reactant is water. The general formula of a hydrolysis reaction is: AB + H2O → AH + BOH Organic hydrolysis reactions involve the reaction of water and a ester. This reaction follows the general formula: RCO-OR' + H20 → RCO-OH + R'-OH Dissolving a salt of a weak acid or base in water is an example of a hydrolysis reaction. Why doesn’t soap form micelles in ethanol as they form in water? A molecule of soap is made up of two parts- a hydrophilic  polar end and a hydrophobic hydrocarbon part.In a soap solution, the hydrocarbon portion of several soap molecules huddle together  whereas the polar ends project outward into the polar solvent, water. These spherical clusters of hundreds of molecules are called micelle. In organic solvent like ethanol, soap is completely soluble, hence no micelle formation Three elements X,Y and Z belong to 17TH group but to 2nd 3th and 4th period respectively. Number of valance electrons in X is 7Find the number of valance electrons in X and Z. Since X, Y and Z all three belong to same group that is 17th therefore they all have same number of valence electrons which is equal to 7. Having different period will not affect on the number of valence electrons provided the group number remain same. The X, Y and Z are Fluorine, chlorine and bromine belonging to 2nd, 3rd and 4th period respectively.   What is the use of oxyacetylene flame? The oxyacetylene flame is a gas torch that burns a mixture of acetylene and oxygen to produce a high-temperature flame (3,000°C or 5,400°F) that can be used for welding, cutting steel, and other metal working. What is observed on adding 5% solution of alkaline potassium permanganate solution drop by drop to some warm ethanol taken in testube. Write the name of the compound formed during chemical reaction. When a 5% solution of alkaline potassium permanganate solution is added drop  by drop to some warm ethanol taken in a test tube, magenta colour of alkaline  potassium permanganate disappears and ethanol has been changed to carboxylic acid . The reaction is as follows. CH3   - CH2OH        --------------- > CH3COOH How would you distinguish experimentally between an alcohol and a carboxylic acid on the basis of a chemical property?         To distinguish experimentally between an alcohol and a carboxylic acid on the basis of a chemical property, we take these samples in two separate test tubes. Add sodium hydrogen carbonate in both the test tubes. The test tube, from which the effectiveness evolves, contain carboxylic acid. The effervescence is due to the evolution of carbon dioxide gas. However, from  test tube containing alcohol there is to effervescence, because no carbon  dioxide gas is produced there. Why are vegetable oils healthy as compared to vegetable ghee ? how are vegetable oils converted into vegetable ghee name the process. The fatty acid with a single double bond is called mono unsaturated fatty acid (e.g. oleic acid), and if it has multiple double bonds, it’s polyunsaturated (e.g. linoleic acid). By virtue of their tightly packed structure, the saturated fatty acids increase the levels of bad cholesterol (LDL) and clog the arteries. On the other hand, the unsaturated fatty acids increase the levels of good cholesterol (HDL) by taking the LDL to the liver to be broken down and removed from the body. Vegetable oil can be converted into ghee by the process of hydrogenation. The process of conversion of oil into ghee is known hydrogenation. This process is called so because hydrogen is added and it takes place at 4500c and with nickel or palladium as a catalyst. CH2=CH2  +H2  ----Ni---------> CH3-CH3 When acetic acid reacts with X, a salt is formed which on reaction with soda lime gives a gas Y. Identify X and Y CH3COOH + NaHCO3 --------------> CH3COONa + H2O +CO2 CH3COONa +NaOH     ---------- ->  CH4 + Na 2 CO3 “Alkenes form a homologous series" Explain.  Homologous series is a group or family of compounds that have the same general formula but vary by a single parameter. Alkenes have general formula, CnH2n and the varying parameter is the length of carbon chain.  C2H4, C3H6, C4H8  are members with different number of carbon atoms.   For more Guess paper visit  CBSE SUMMATIVE ASSESSMENT-II SAMPLE PAPER 2014 Class Xth [Links] CBSE SUMMATIVE ASSESSMENT-II SAMPLE PAPER 2014 Class IXth [Links] Sample Paper Mathematics Sample Paper Mathematics Sample Paper Science Sample Paper Science Sample Paper Hindi, English and Sanskrit Sample Paper Hindi, English and Sanskrit Sample Paper Social Science Sample Paper Social Science

Soaps - preparation of soaps - Detergents - advantages and disadvantages

10th Chemistry : Soaps and Detergents [Carbon and Its Compound]

 SOAPS

Metallic salts prepared from natural fats are called soaps. Soap is a sodium salt or potasium salt of long chain fatty acids that has cleansing action in water. Sodium stearate, sodium oliate and sodium  palmitate are some examples of soaps.

Stearic acid is a long chain fatty acid. Its formula is C₁₇H₃₅COOH. This reacts with sodium hydroxide to give a compound called sodium stearate, which has properties of soap.

Similarly, sodium hydroxide reacts with oleic acid and palmitic acid forming sodium oleate   (C₁₇H₃₃COONa) and sodium palmitate (C₁₇H₃₁COONa) respectively.

Please Note!

Fatty acids are organic compounds. The molecules of these compounds contain a carboxyl  group                 {-COOH}. These molecules react with a trihydric alcohol called glycerol to form a class of compounds called esters.

Groundnut oil, coconut oil, palm oil, caster oil, gingely oil, animal fat etc are all esters of fatty acids. Fats and fatty oils are called glyceryl esters or tglycerides.

PREPARATION OF SOAP

Experiment : Take about 30 ml of a vegetable oil in a beaker. Add about 60ml of 20% sodium hydroxide solution to it. Heat slowly until the mixture boils. After 5-10 minutes of boiling, add about 5g of sodium chloride to separate soap from the solution. Cool the solution. Observe the creamy layer of soap floating on the  solution.

We need animal fat or vegetable oil, sodium hydroxide and sodium chloride for preparing soap. Fat or vegetable oil is a glyceride or a glyceryl ester. Soap is prepared by hydrolyzing fat or oil with bases such as sodium hydroxide or potassium hydroxide. This process of preparing soap is called saponification.

When a mixture of a oil/fat and a strong solution of sodium hydroxide is boild in an iron tank, a sodium salt of the fatty acid and glycerol are formed. The sodium salt of the fatty acid thus formed is nothing but soap.

Please Note!

A Swedish chemist, Carl Wilhelm Scheel, discovered accidentally the process of preparation of soap in 1783. He boiled olive oil with lead oxide and obtained a sweetish substance which was seat to taste. This substance is now known as glycerine.

Oil/fat + sodium hydroxide ----->  soap + glycerol

                                   Fig-01

Please Note! 

Glycerol

Glycerol is a sweet viscous liquid soluble in water. It is a byproduct of saponification process. It is commonly called glycerine. Its formula is CH₂OH.CHOH.CH₂OH. It is used in the manufacture of explosives, plastics, and pharmaceuticals. It is also used to prevent freezing.

Soap thus formed is separated with the help of sodium chloride. Addition of sodium chloride reduces the solubility of soap considerable. Soap, being lighter, floats like a cream on the solution. It is separated from the solution; suitable chemicals of suitable colour and odour are added to it and cast into moulds. When soap cools and solidifies, it is cut into desired shapes and packed. Glycerol exists in dissolved state in the solution. It is separated by distillation.

How does soap clean

Soap dissolves in water. This is due to the contrasting properties of the ends of the soap molecules.

A soap molecule has a long hydrocarbon end [E.g. CH₃(CH₂)₁₆] and a short ionic end containing COONa⁺.  The non-ionic hydrocarbon end has the property to repel water. The other end, which is ionic, has the property to attract water. This end attaches itself to water. The hydrocarbon end attaches to the dirt or grease to form structures called ‘micelles’.

                                                                           Figure-02

In micelles soap molecules are arranged radially. The end attached to water pulls out the dirt from the fabric. This can be washed off with water.

DETERGENTS

The term detergent is derived from a Latin word which means surface active. Synthetic detergents are commonly known as detergents. Detergents are also called soap less soaps.

Detergents do not form insoluble ‘scum’ with magnesium and calcium ions present in hard water. Therefore, detergents clean better than soap even in hard water.

Detergents are sodium salts of long chain benzene sulphonic acid or sodium salts of long chain alkyl hydrogen sulphate. A detergent molecule consists of a large hydrocarbon group that is non-ionic and a sulphonate (SO₃^- Na⁺) or a sulphate (SO₄^- Na⁺)  group that is ionic. Sodium n-dodecyl benzene sulphonate and Sodium dodecyl sulphate are two well-known detergents.

Note:

Long chain hydrocarbons obtained from petroleum are treated with concentrated sulphuric acid. The organic acids produced during this process are neutralized with sodium hydroxide. The sodium salt obtained is a detergent.

ADVANTAGES OF DETERGENTS OVER SOAPS

Detergents have more advantages than soap. Therefore, detergents are more widely used than soap. Let us now turn our focus towards the advantages of detergents.

! Detergents cleanse well even in hard water. Soap is not so good for washing when water is hard.

! Detergents are made from hydrocarbons obtained from petroleum. Soap is prepared from vegetable oil or animals fat that are usually edible. Detergents are not bio-degradable. Soaps are biodegradable.

! Detergents cleanse well even in acidic medium. Soap does not cleanse well in such a medium.

Detergents have their disadvanges.

! Detergents are not bio-degradable. They polutes water and soil.

Total Fatty Matter (TFM)

 Soaps are graded in terms of total fatty matter or TFM. Bureau of Indian Standards (BIS) has catogorised bath or toilet soaps as ‘normal’, ‘baby,  transparent, and antibacterial soaps. The last three are called specialty soaps  targeted to specific users. A toilet soap is a cosmetic by law and it must fulfil the  requirements of the relevant Indian standard.

 T. F. M or total fatty matter is a measure for identifying the amount of fatty matter  present in soaps. TFM of a sample of soap can be determined as follows. A known  weight of the soap is dissolved in water and the solution is treated with dilute  sulphuric acid. The soap decomposes to sodium suplphate and fatty acids. The fatty acids so formed can be estimated. From this TFM can be calculated. On the  basis TFM, toilet soaps can be classified into three grades.  

Grade	TFM	Moisture		Free salt (NaCl)
I	above 80	Max :	13.5	Max :	0.7
II	65 – 80		13- 15		0.8
III	55- 65		15-20		1.5

Q. Swapnesh, living in Ooty, was washing clothes in cold water. He found that  the clothes were not getting clean. Geeta , his niece, suggested that he wash  the clothes in warm water. Washing of clothes with soaps or detergents is  easier in Luke warm water than cold water.

(a)Why?

(b) What value do you derive from this?

Ans:

(a) Action of soaps is due to formation of micelles. But the formation of micelles takes place at a minimum temperature called ‘Kraft  temperature’. This temperature is reached in lukewarm water.

(b) Be humble to accept a scientific fact from a younger person