Carbon and its compounds CBSE Solved Test Paper

Q. 1. How much percentage of earth’s crust constitutes carbon element ?

Ans. The earth’s crust has only 0·02% of carbon in the form of minerals.

Q. 2. What do you mean by covalency ?

Ans. Covalency is defined as the number of electrons shared by an atom.

Q. 3. What is covalent bond ?

Ans. A bond formed by the sharing of electrons is called covalent bond. 

Q. 4. What is functional group ?
Ans. A functional group is an atom or a group of atoms that characterizes the chemical properties of an organic compound.

Q. 5. What is organic chemistry ?

Ans. The branch of chemistry that deals with study of compounds of carbon except for oxides of carbon, carbonate and hydrogen carbonate salts is called organic chemistry.

Q. 6. What are Hydrocarbons ?

Ans. These are the compunds of carbon and hydrogen are called hydrocarbon.

Q. 7. What are saturated carbon compounds ?

Ans. The compunds of carbon in which carbon-carbon atoms are linked by single covalent bond are called saturated carbon atoms; Alkanes.

Q. 8. What are unsaturated carbon compunds ?

Ans. The compounds of carbon in which carbon-carbon atoms are linked by multiple bonds i.e. double or triple bonds are called unsaturatedcarbon compounds, e.g : Alkenes or Alkynes.

Q. 9. Define Allotropy.
Ans. The phenomena by virtue of which an element can exist in two or more than two forms having similar chemical properties but different physical properties is called allotropy.

Q. 10. What is vinegar ?
Ans. Vivegar is 5–8% solution of acetic acid in water.

SHORT ANSWERS TYPE QUESTIONS   2 Marks each 

1.What is combustion ?
Ans. It is the process of burning of a substance in the presence of oxygen to produce carbon dioxide along with heat and light.Combustion reactions are also called oxidation reactions.
e.g. : CH4 + O2 ——> CO2 + H2O + Heat and light

2. Write two differences between oils and fats.
Ans. Oils : 1. Oils are liquid at room temperature 2. Oils contaning unsaturated fatty acids.
        Fats : 1. Fats are solid at room temperature.    2. Fats containing saturated fatty acids. 

3. Define Esterification ?
Ans. It is the process of formation of ester by the reaction between an alcohol and an acid is called esterification. e.g. : Reaction between ethanol and ethanoic acid in presence of conc. H2SO4.
CH3COOH        +        C2H5OH ——> CH3COOC2H5 + H2O
Ethanoic acid               Ethanol                Ethylethanoate      Water 

4. What is saponification ?

Ans. It is the alkaline hydrolysis of esters to give back the carboxylic acid and alcohol. As it is used in the prepation of soap, it is called saponification.
CH3COOH     +      NaOH             ——> CH3COONa           +       C2H5OH
Ethanoic acid     Sodiumhydroxide             Sodiumethanoate                Ethanol

5. Which of the following hydrocarbons undergo addition reactions :
C2H6, C3H8, C3H6, C2H2and CH4.

Ans. Unsaturated hydrocarbons, i.e., Alkenes and alkynes undergo addition reactions. Alkenes and alkynes have general formula CnH2n and CnH2n -2. 

Thus compounds — C3H6 (propene) and, C2H2 (ethyne) ; undergo addition rections.

6. How can you differentiate saturated and unsaturated Hydrocarbon on the basis of burning behaviour ?
Ans. On burning, saturated hydrocarbons give a clean flame whereas unsaturated Hydrocarbons on heating give a yellow flame with lots of black smoke. 

7. Write two ill-effects of drinking excess of alcohol ?
Ans. (1) Alcohol causes addiction and makes person dependent on it.
(2) If consumed in large quantities, it may cause death by damaging liver.

8. What is denatured alcohol ?
Ans. Alcohol which is made unfit for the drinking purposes is called denatured alcohol. It is ethyl alcohol (C2H5OH) mixed with poisonous substances like methanol, copper sulphate, etc.

9. Give two advantages of synthetic detergents over soaps ?
Ans. (1) Synthetic detergents can be used with hard water also whereas soaps cannot with hard water.
(2) Synthetic detergents are more soluble and have better cleansing action than soaps.

10. What are substitution reactions ?
Ans. It is a type of reaction in which a chemical reagent (substituent) displaces the another atom or group (leaving group) in a compound, e.g., Substitution of Hydrogen of Methane by chlorine

CH4           + Cl₂         --Sunlight ---------->       CH₃Cl              +              HCl 

Methane    Chlorine                                       Methyl Chloride           Hydrogen Chloride 

                                                                              or
                                                                      Chloramethane

SHORT ANSWERS TYPE QUESTIONS 3 Marks each

1. Differentiate between diamond and graphite.

Ans. Diamond :

1. Diamond has 3-dimensional network structure.
2. Each carbon in diamond is bonded to four other carbon atoms.
3. No free electron is left.
4. It is a bad conductor of electricity.
5. It is hard.

Graphite :

1. Graphite has hexagonal sheet layer structure.
2. Each carbon atom in graphite is bonded to three other carbon carbon atoms.
3. Each carbon has one free electron with it.
4. It is a good conductor of electricity.
5. It is soft and slippery.

2. How is combustion different from pyrolysis ?

Ans. Combustion means heating a compound in the presence of excess or limited supply of air, e.g., combustion of methane gives carbon dioxide and water.
CH4 + O2 ——> CO2 + H2O + Heat and light.
Pyrolysis means the decomposition of a hydrocarbon into its element on strong heating in the absence of air, e.g. : Pyrolysis of methane gives carbon and hydrogen.
CH4               ------100°C-------------> C + 2H2
                            In abesebce of air

3.Discuss the method of preparation of soap in the laboratory.

Ans. In laboratory, soap is prepared by heating of equal volumes of castor oil and concentrated sodium hydroxide solution taken in a beaker. A paste of soap is formed by constant stirring during heating. Most of the soap separates out but some of it remains dissolved in solution. NaCl is then added to precipated out all the soap from equeous solution. On cooling the solution, solid soap separates out.
Glycerl Oleate + Sodium ---Heat -> Sodium Oleate + Glycerol
 Glycerol is obtained as a byproduct in this process.

4. Write five ill effects of alcohol drinking.

Ans. (1) Alcohol is an intoxicant and its drinking result lose in the sense of discrimination.
(2) It ruins the health of the person by damaging liver and making his brain dull.
(3) Alcohol drinking by the head of a family worsens the economic condition of the family.
(4) The alcohol drinking by the head of a family has very bad effect on the psychological development of the children.
(5) Drinking adulterated alcohol causes blindness or even death.

5. Differentiate between soaps and synthetic Detergents.

Ans. Differences between soaps and synthetic detergents :

Soaps :

1. They are the sodium salts of the long chain carboxylic acids. The ionic group in soaps is – COO Na
2. Soaps have relatively weak cleansing action.
3. Soaps are prepared from animal fats or vegtable oils.
4. They are not suitable for washing clothes in Hard water.
5. Soaps are biodegradable.

Synthetic Detergents :

1. Synthetic detergents are the sodium salts of long chain benzene sulphone acids or long chair alkyl hydrogen sulphate. The ionic group in a synthetic detergent is — SO3Na or —SO4—Na+.
2. Synthetic detergents have a strong cleasing action.
3. Synthetic detergents are prepared from the hydrocarbons.
4. Synthetic detergents can be used for washing clothes even in Hard Water.
5. Synthetic detergents are non-biodegradable.

6. Differentiate between ionic compounds and covalent compounds.

Ans. Difference between ionic compounds and covalent compounds :

Ionic compounds :

1. Ionic compounds have constituents particles called ions.
2. In these compounds the ions of opposite charge are held together by strong electrostatic forces of attraction.
3. They have high melting and boiling points.
4. These conduct electricity in solution or in molten state.

Covalent compounds :

1. Covalent compounds have constituent particles called molecules.
2. In these compounds the molecules are held together by weak attractive forces.
3. They have low melting and boiling points.
4. These are largely non-conductor.

7. Give some important properties of ethanol (ethyl alcohol).

Ans. (1) Ethanol (C2H5OH) is highly soluble in water.
(2) It is a colourless liquid at room temperature.
(3) It has very low melting point (156 K).
(4) It has low boiling point (351 K or 78ºC).
(5) It is one of the main components of alcoholic drinks.
(6) It is a good organic solvent.
(7) Ethanol alcohol reacts with Na metal vigorously to evolve H2 gas.
2C2H5OH + 2Na ——> 2C2H5ONa + H2 (g)
Sodium ethoxide
(8) It burns with blue flame in the presence of O2 of air. This combustion is an oxidation process.
C2H5OH + 3O2  -Combustion ----->2CO2 + 3H2O + Heat and light 

8. Give five main advantages of synthetic detergents over soaps.

Ans. Following are the advantages of synthetic detergents :
1. Synthetic detergents can be used even with hard water but soaps cannot be used with hard water.
2. Synthetic detergents have a stronger cleansing action than soaps.
3. Synthetic detegents are more soluble in water than soaps.
4. Synthetic detergents are prepeard from the hydrocarbons white soaps are prepared from from animal fat or vegetable oil which leads to their deficiency for human consumption.
5. Synthetic detergents can be used even in acidic solution but not the soaps.

9. Write important uses of (a) ethanol and (b) ethanoic acid.

Ans. (a) Uses of ethanol :

(1) Ethanol (ethyl alcohol) is used for making alcoholic drinks like wines, whiskies, beer, etc.
(2) It is used for making wood polish.
(3) It is used for making some medicines like cough syrups, tincture iodine and some tonics.
(4) It is used for making antifreeze material for cooling engines of vehicles.

(b) Uses of ethanoic acid :

(1) Dil. solution of ethanoic acid (acidic acid) in water is called vinegar, which is used as a preservative of pickles.
(2) It is used as a useful reagent in the chemical laboratories.
(3) It is used for making many C– compounds.
(4) It is used for making esters which are used as flavouring agents and perfumes.

10. What happens when ethanol reacts with   (i) sodium     (ii) potassium permanganate solution.

Ans-(i) with sodium metal ,sodium ethoxide formed.

2CH3CH2OH+2Na ------------> 2CH3CH2ONa + H2

(ii) With alkaline potassium permanganate, ethanol is oxidised to ethanoic acid.

CH3CH2OH+2[O] --------> KMnO4 ---Dil.H2SO4 -----> CH3COOH + H2O

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VERY SHORT ANSWER QUESTIONS

1. How many covalent bonds are present in ethane , C2H6 .

2. What do you mean by catenation ?

3. Name the simplest hydrocarbon .

4. Which functional group is 
present in (a) Methanal (b) Propanone ?

5. Draw electron dot structure of the first member of alcohol homologous series.

6. Give name and formula of simplest ketone .

7. What is absolute alcohol ?

8. Write the structure and name of compound A in the following reaction :
CH3 CH2 OH ------------> A+H2O

9. Name and give formula for higher homolog of ethanol .

10. What do you mean by octet rule ?

11. Differentiate between soaps and detergents on the basis of their chemical composition .

12. What is glacial acetic acid ?

13. Draw the structure of a micelle .

14. Which of the following hydrocarbons will give addition reaction ?

C2H6 , C3H8 , C3H4 , C2H4

15. Give a chemical test to distinguish between Ethane and ethane.
Short answer questions
1. Explain the nature of covalent bond using the bond formation in CH3Cl

2. What are isomers ? explain with an example.

3. What are hydrocarbons ? Give general formulaes of alkanes , alkenes , and alkynes

4. What is homologous series ? Give its characteristics .

5. State two conditions under which hydrocarbons give sooty flame on combustion.

6. How will you diffrentiate ethane and ethanoic acid by a simple chemical test ? Also draw electron dot

structure for these two .

7. What do you mean by (a) Denatured alcohol (b) Glacial acetic acid ?

8. Explain the following reactions (a) Esterification (b) saponification .

9. A brisk effervescence is produced when a piece of sodium metal is added to ethanol . 
(a) write the   chemical equation for reaction 
(b) Name the gas evolved . How will you test this gas ?

10. Why are carbon and its compounds used as fuels ?

11. How ethanol and ethanoic acid can be differentiated on the basis of their physical and chemical

properties ?

12. What happens when etanoic acid is 

(a) treated with sodium bicarbonate (b) heated with conc. H2SO4

(c) heated with ethanol in the presence of conc. H2SO 4 ? Give equations .

13. Explain following reactions of carbon compounds ? (a) addition reaction (b) oxidation (c) substitution .

14. What is a covalent bond .Describe the formation of O2 and N2 .

15. An organic compound X is an essential constituent of wine and beer . Oxidation of X yields an 
organic acid Y which is present in vinegar . Name the compounds X and Y . Also write their formulae.

Long answer questions

1. (a) Explain cleansing action of soap ? (b) Differentiate between soaps & detergents.

2. Explain formation of scum when soap reacts with hard water.Why is detergent a better cleansing agent 
 than soap?

3. (a) Why does carbon form compounds mainly by covalent bonding ? (b) List any two reasons for
carbon forming very large number of compounds ?

4. Name the class of organic compounds to which CH 3 - CH = CH 2 belongs . Give its IUPAC name .
Which product is formed when this compound is treated with H2 in the presence of nickel catalyst .also
give name and formula of higher homolog of CH 3 - CH= CH2

5 Two compounds A & B have molecular formulae C3H6 & C3H8 respectively, which one is likely to 
show addition reaction ? Giive an equation to show how addition reaction is useful in making vegetable
ghee.

6. An organic compound 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 conc. sulphuric 
acid , a compound Y is formed , which is having sweet smell.
(a) Identify X & Y.  (b) Write a chemical equation for the reaction

Xth Chemistry - Carbon and its Compounds (Sample Board Guess Questions paper)

1 mark questions:-

1. Name the type of bond formed when sharing of electrons occurs.

2. How many valence electrons are there in valence shell of carbon atom?

3. Define catenation.

4. What do you understand by unsaturated 

compounds?

5. Why are unsaturated hydrocarbons more reactive  than saturated hydrocarbons?

6. What is the difference in number of carbon and hydrogen atoms between two successive members of a homologous series?

7. What is the difference in molecular masses of any two successive homologues?

8. Name the functional group present in following compounds:-
(i) C2H5OH (ii) CH3COC2H5

9. Give the IUPAC name of the following compounds.
(a) CH3 −CH2 −Cl
(b)   H −C = O
              I
            H

10. Substitution reactions are given by which type of hydrocarbons?

11. Name the type of hydrocarbon taking part in an addition reaction.

12. Name the products obtained from the complete combustion of saturated hydrocarbon.

13. Acetic acid is also known as glacial acid. Why?

14. Which gas evolved when sodium carbonate reacts with ethanoic acid?

15. Name the catalyst commonly used in the process of conversion of vegetable oils into fats.

16. Write the colour of flame produced by unsaturated hydrocarbons on complete combustion.

17. Which acid is regarded as dehyderating agent?

18. What are hetro atoms? Give one example.

2 marks questions:-

19. Draw electron dot structure of CH4 and O2.

20. What is a homologous series? Write two main features of homologous series.

21. Explain why saturated hydrocarbons give sooty flame on incomplete combustion?

22. Differentiate between saturated and unsaturated hydrocarbons giving one example of each.

23. Which of the following hydrocarbons undergoes addition reactions & why :-

C2H6, C2H2, C3H8, C3H6

24. Write the chemical formula and structural formula of:- (i) Benzene  (ii) Propanoic acid

25. Write names of following compounds as per nomenclature:-

(i) CH3CH2COOH (ii) CH3CH2COCH

26. What are structural isomers? How many structural isomers can you draw from Pentane?

27. What is hydrocarbon? Write the general formula of the hydrocarbons :-

(i) Alkane (ii) Alkene (iii) Alkyne

28. What happens when a piece of sodium is dropped into a test tube containing ethanol? Write the chemical equation also.

29. A hydrocarbon compound A is active ingredient of wine and cough syrups. A on oxidation with acidified K2Cr2O7 forms compound B. Identify the compound A and B and write the chemical equations involved.

30. What is hydrogenation? Write its industrial application.

31. Which type of reaction takes place when saturated hydrocarbons react with chlorine in presence of sunlight? Write the chemical equation if the saturated hydrocarbon is methane(CH4).

32. What is scum? How is it formed?

33. A, B and C are members of a homlogous series, there melting points are–183⁰  C,–138⁰ C and  –130⁰ C respectively. Among these:-
(i) Which member will have least number of carbon atoms?
(ii) Which member will have maximum number of carbon atoms?

34. What are esters? How are they formed?
3 marks questions:-

35. Write the chemical formula and structure of the following:-
(i) Cyclohexane (ii) Propanal (iii) Chlorobutane

36. Draw the electron dot structure of the following:-
(i) C2H6 (ii) C2H4 (iii) C2H2

37. Giving chemical equations of the reactions write what happens when:-
(i) Ethanol is heated at 443K with excess of concentrated sulphuric acid.
(ii) Conversion of oils (unsaturated hydrocarbon) into fats (saturated hydrocarbons)
(iii) Ethanoic acid reacts with sodium hydroxide.

38. Draw three structural isomers butane.

39. Explain formation of micelles with the help of suitable diagram?

40. Explain the following terms with related chemical equations:-
(i) Dehydration
(ii) Esterification
(iii) Saponification

41. Soap does not work effectively in hard water. Explain why?

42. How can you obtain the following from pure ethanol :-
(i) Ethene
(ii) Ethanoic acid
(iii) Ester
Write the chemical equations of the reactions.

43. Distinguish between addtion and substitution reactions with suitable examples.

44. Differentiate between ethanol and ethanoic acid on basis of following test:-
(i) Blue litmus test
(ii) Reaction with sodium bicarbonate
(iii) Sodium metal test.

45. Give reasons for the following observations :–
(i) The element carbon forms a very large number of compound.
(ii) Air holes of a gas burner have to be adjusted when the heated vessels get blackened
by the flame.
(iii) Use of synthetic detergents cause pollution of water.

46. What is the difference between combustion and oxidation?
Under what condition an oxidation reaction can be cancelled as combustion? [Illustrate your answer with one example each.]
5 marks questions:-

47. What are soaps? Explain the mechanism of the cleaning action of soaps?

48. Soaps form  scum (insoluble substance) with hard water. Explain why? How this problem is overcome  by use of  detergents?

49.Give one example of each of the following :–
(a) A carbon compound containing two double bonds.
(b) A molecule in which central atom is linked to three, other atoms.
(c) A compound containing both ionic and covalant bonds.
(d) An organic compound which is soluble in water.
(e) A carbon compound which burns with a sooty flame.

50. Why is the conversion of ethanol to ethanoic acid considered an oxidation reaction?  [2011 (T-II)]

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IUPAC Rules for Naming Hydrocarbons

1.Choose the correct ending: - ane, - ene, or - yne


2.Determine the longest carbon chain. Where a double or triple bond is present, choose the longest chain that includes this bond. If there is a cyclic structure present, the longest chain starts and stops within the cyclic structure.


3.Assign numbers to each C of the parent chain. For alkenes and alkynes the first carbon of the multiple bond should have the smallest number. For alkanes the first branch (or first point of difference) should have the lowest . Carbons in a multiple bond must be numbered consecutively.


4 .Attach a prefix that corresponds to the number of carbons in the parent chain. Add cyclo- to the prefix if it is a cyclic structure.


5.Determine the correct name for each branch (“alkyl” groups include methyl, ethyl, propyl, etc.)


6.Attach the name of the branches alphabetically, along with their carbon position, to the front of the parent chain name. Separate numbers from letters with hyphens (e.g. 4-ethyl-2-methyldecane)


7.When two or more branches are identical, use prefixes (di-, tri-, etc.) (e.g. 2,4-dimethylhexane). Numbers are separated with commas. Prefixes are ignored when determining alphabetical order. (e.g. 2,3,5-trimethyl-
4-propylheptane)


8.When identical groups are on the same carbon, repeat the number of this carbon in the name. (e.g. 2,2-dimethylhexane)

Naming Side Chains

Example: use the rules to name the following structure

Rule 1: choose the correct ending

Rule 5: Determine name for side chains               1-hexene

Rule 6: attach name of branches alphabetically    2-ethyl-4-methyl-4-methyl-1-hexene

Rule 7: group similar branches                             2-ethyl-4,4-dimethyl-1-hexene

Practice

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THE MODERN PERIODIC TABLE 10th chemistry

THE MODERN PERIODIC TABLE 10th chemistry

The modern version of the periodic law is stated as :
“The physical and chemical properties of the elements are the periodic functions of their atomic masses”.
LONG FORM OF THE PERIODIC TABLE
There are many forms of the periodic tale. The long form of the periodic table is the most convenient and the most widely used and is presented here. The horizontal rows are called PERIODS. Elements having similar chemical and physical properties appear in vertical columns and are known as GROUPS or FAMILIES. Altogether there are seven periods and 18 groups.
PERIODS
1ST Period Contain only 2 elements namely 1H, 2He and is the shortest period.
IInd Period Contains 8 elements namely 3Li, 4Be, 5B, 6C, 7N, 8O, 9F and 10Ne is known as the short period.
IIIrd Period Contains 8 elements : 11Na, 12Mg, 13Al, 14Si, 15S, 16S, 17Cl, and 18Ar. The IIIrd period is also known as short period.
IV Period starts with potassium and contains 18 elements : 19K, 20Ca, 21Sc, 22Ti, 23V, 24Cr,
25Mn, 26Fe, 27Co, 28Ni, 29Cu, 30Zn, 31Ga, 32Ge, 33As, 34Se, 35Br and 36Kr and is known
as long period.
V Period Starts with rubidium and contains 18 elements : 37Rb, 38Sr, 39Y, 40Zr, 41Nb, 42Mo, 43Tc,
44Ru, 45Rh, 46PD, 47Ag, 48CD 49In, 50Sn, 51Sb, 52Te, 53I, 54Xe.The fifth
VI Period Consists of 32 elements, starting from cesium (55Sc) and ending with radon. It is
called as longest period. This period includes the 4f shell that includes Lanthanides
(58Ce, …..71Lu).
VII Period Like the sixth period would have a theoretical maximum of 32 elements. This period
however is incomplete and at present contains 19 elements starting from 87Fr
(francium) to 92U. All these elements are naturally occurring but rest are radioactive with very short half lives. These also include a part of inner transition elements, 90Th, …. 103Lr.
GROUPS
The atom of the element in a single vertical column have the same or very similar electronic configurations in the highest occupied orbitals and are therefore said to belong to the same
GROUP or FAMILY of elements. According to the new IUPAC recommendations the groups are numbered form 1 to 18. Bases on the electronic configuration, we can classify elements in to four types.
1. Noble Gases
2. Representative Elements
3. Transition Elements and
4. Inner Transition Elements
1. Noble Gases

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9th chemistry Self-evaluation on Mole concept

Sample Problem 1. Calculate the number of mole in 52 g of Helium.

Solution. We know that, Atomic mass of He = 4u

So, its molar mass = 4 g  That is, 4 g of He contains 1 mole of He.

Or, 4 g of He = 1 mole of He

Or, 1 g of He = 1/4 mole of He

So, 52 grams of Helium =1/4 x 52 mole = 13 moles

Therefore, there are 13 moles in 52 g of He

Sample Problem 2. Calculate the number of moles for 12.044 X 10²³ atoms of Helium.

Solution: 

6.022 X 10²³ atoms of Helium           = 1 mole

1 atom of Helium                                 =1/6.022 X 10²³ mole

12.044 X 10²³ atoms of Helium         = [(1/6.022 X 10²³) x  12.044 X 10²³  ]moles

[ You may use  ----        Number of moles    = (given numbers of particles /Avogadro number)]

Sample Problem 3. How many moles are there in 5 grams of calcium?

Sample Problem 4. How many moles there in 12.044 X 10²³ atoms of phosphorous?

Sample Problem 5. Calculate the mass of 0.5 mole of Nitrogen atoms.

Solution. We know that, Molar mass of of Nitrogen atoms 14 g

The mass of 1 mole of Nitrogen atoms = 14 g

The mass of 0.5 mole of Nitrogen atoms = 14x 0.5 g = 7 g

Alternate method,

                        Mass = Number of moles X Molar mass

                  Or,           = 0.5 X 14 = 7 g

Therefore, mass of 0.5 mole of N atoms is 7 grams.

Sample Problem 6. What is the mass of 3.011 X 10²³ number of Nitrogen atoms?

Solution. We know that, Molar mass of of Nitrogen atoms 14 g

The mass of   6.022 X 10²³ number of Nitrogen atoms= 14 g

The mass of  3.011 X 10²³ number of Nitrogen atoms = [(14g/6.022 X 10²³ )x 3.011 X 10²³]g = 7 g

Sample Problems 
Sample Problem 7. Calculate the number of particles in each of the following:

(i) 0.1 mole of Carbon atoms  (ii) 46 grams of Sodium atoms.

Sample Problem 8 What is the mass of 4 moles of Aluminum atoms?

Determine the number of iron atoms in a piece of iron weighing 2.8 grams.

Sample Problem 9 If one mole of Carbon atoms weigh 12 grams, what is mass in grams of a single atom of Carbon?

Sample Problem 10. Calculate the mass of 0.5 mole of N2 gas.

Sample Problem 11. Convert 12.044 X 10²² molecules of Sulphur dioxide into moles?

Sample Problem 12. In which case the number of Hydrogen atoms is more- 2 mol of HCl or 1 mol of NH3?

Sample Problem 13 . An ornament of silver contains 20 gram silver. Calculate the moles of silver present.

Sample Problem 14. If 1 g sulphur dioxide contains x molecules, what will be the number of molecules in 1 g of methane?

Sample Problem 15. Calculate the number of aluminium ions present in 0.051 g of aluminium oxide.

Sample Problem 16. How many grams of neon will have the same number of atoms as 4 g of calcium?

Sample Problem 17. Calculate the number of iron atoms in a piece of iron weighing 2.8 grams.

Sample Problem 18. What is the mass of 3 moles of Zinc?

Sample Problem 19 : What is the ratio of molecules present in 6.6 grams of CO2 and 3.2 grams of SO₂?

Sample Problem 20. If one gram of Sulphur contains x atoms, what will be the number of atoms in one gram of oxygen? (atomic mass of S = 32u) 

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IX CBSE Chapter - Atoms and molecules E-Notes

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Empirical formula and molecular formula Study Notes

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Determining Empirical formula and molecular formula

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9th chemistry Self-evaluation on Mole concept

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Numerical based on mole concept 9th Chemistry

Numerical problems based on mole concept 9th Chemistry

1. Calculate the number of moles of magnesium present in a magnesium ribbon weighing 12 g. Molar atomic mass of magnesium is 24g/ mol

2. Verify by calculating that

(a) 5 moles of CO² and 5 moles of H₂O do not have the same mass.

(b) 240 g of calcium and 240 g magnesium elements have a mole ratio of 3:5.

3. Find the ratio by mass of the combining elements in the following compounds.

(a) CaCO₃ (b) MgCl₂ (c) H2SO4 (d) C2H₅OH (e) NH₃ (f) Ca(OH)₂

4. Calcium chloride when dissolved in water dissociates into its ions according to the following equation.  CaCl₂ (aq) → Ca₂+ (aq) + 2Cl– (aq)

Calculate the number of ions obtained from CaCl₂ when 222 g of it is dissolved in water.

5. The difference in the mass of 100 moles each of sodium atoms and sodium ions is 5.48002 g. Compute the mass of an electron.

6. Cinnabar (HgS) is a prominent ore of mercury. How many grams of mercury are present in 225 g of pure HgS? Molar mass of Hg and S are 200.6 g /mol and 32 g/ mol respectively. 

7. The mass of one steel screw is 4.11g. Find the mass of one mole of these steel screws. Compare this value with the mass of the Earth (5.98 × 10²⁴kg). Which one of the two is heavier and by how many times?

8. A sample of vitamin C is known to contain 2.58 ×10²⁴ oxygen atoms. How many moles of oxygen atoms are present in the sample?

9. Compute the difference in masses of 103 moles each of magnesium atoms and magnesium ions. (Mass of an electron = 9.1×10^–31 kg)

10. Compute the number of ions present in 5.85 g of sodium chloride.

11. A gold sample contains 90% of gold and the rest copper. How many atoms of gold are present in one gram of this sample of gold?

12. Compute the difference in masses of one mole each of aluminium atoms and one mole of its ions. (Mass of an electron is 9.1×10^–28 g). Which one is heavier?

13. A silver ornament of mass ‘m’ gram is polished with gold equivalent to 1% of the mass of silver. Compute the ratio of the number of atoms of gold and silver in the ornament.

14. A sample of ethane (C2H6) gas has the same mass as 1.5 ×10²⁰ molecules of methane (CH₄). How many C₂H₆ molecules does the sample of gas contain?

15. Fill in the blanks

(a) In a chemical reaction, the sum of the masses of the reactants and products remains unchanged. This is called ————.
(b) A group of atoms carrying a fixed charge on them is called ————.

(c) The formula unit mass of Ca₃ (PO₄)₂ is ————.

(d) Formula of sodium carbonate is ———— and that of ammonium sulphate is ——

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