3 MARK QUESTIONS for Class 10 CHEMISTRY

CHEMICAL REACTIONS AND EQUATIONS

Q1. State one example each along-with the chemical equation characterised by the  following:

(i)  Change in state  

(ii) Evolution of gas

(iii) Change in temperature             

Q2. Balance the following chemical equations along with the symbols of physical states of all the reactants and the products:-

(i) Pb3O4 +HNO3 → Pb(NO3)2 + PbO2 +H2O

(ii)  C2H5OH + O2 → CO2  + H2O + Heat

(iii)  Pb3O4  + HCl→ PbCl2 + Cl2 + H2O

Q3. Study the reactions given and indicate which of the following chemical reactions will occur with suitable reason for each.

(i)  Zn(s) + CuSO4 (aq) → ZnSO4 (aq) + Cu(s)

(ii)  Fe(s) + ZnSO4(aq) → FeSO4 (aq) + Zn(s)

(iii)  Zn(s)  + FeSO4 (aq) → ZnSO4 (aq) + Fe(s)

Q4. What is a Redox reaction? Identify  the substances that  are  oxidised  and  the substances that  are reduced  in  the following  reactions:

(i) Fe2O3 +2Al → Al2O3 +2Fe

(ii) 2PbO+ C → 2Pb     + CO2   

Q5.  On heating blue coloured powder of Copper  (II)  Nitrate in a boiling tube,  Copper Oxide (black), Oxygen gas and a brown gas X are formed.

(i) Write a balanced chemical equation of the reaction.             ,

(ii)  Identify the brown gas X evolved.

(iii)   Identify the type of reaction.

(iv)  What could be the pH range of the aqueous solution of the gas X?

Q6.         (a) Mention the four type of information given by an equation.

               (b) State the law of conservation of mass as applicable in a chemical reaction.

Q8. Give reasons:

(i) All decomposition reactions are endothermic reactions.

(ii) Colour of Copper Sulphate solution changes when an iron nail is dipped in it.

(iii) Respiration is an exothermic reaction.

Q9. Write the chemical equation when:

(i) Dilute hydrochloric acid is added to solid Sodium Carbonate.

(ii) Quicklime is treated with Water.

(iii) Sodium chloride solution is added to Lead Nitrate solution.

Q10. 2g of ferrous sulphate crystals are heated in a boiling tube. Answer the following

(i) Write the colour of Ferrous Sulphate crystals both before heating and after heating.

(ii) Name the gases produced during heating.

(iii) Write the chemical equation for the reaction.

Q11. Identify the colour and chemical name of the substance of coating in silver, copper and iron when they are exposed to air.

Q12. Write an example  in each of the following case to support that :

(i) Corrosion of some metals is an advantage.

(ii) Corrosion of a metal is a serious problem.

Q13. Name the salts that are used in black and white photography.   Write the reactions when they are exposed to light. Define the type of chemical reaction taking place.

Q14. What information do we get from a balanced chemical equation?

Q15.  In a container, solid calcium oxide was taken and water was added slowly to it.

(a) State the two observations made in the experiment.

(b) Write the name and chemical formula of the product formed

Q16. Give reasons:

(a) Magnesium ribbon should be cleaned before burning in air.

(b) Photosynthesis is considered as an endothermic reaction.

(c) Combustion reaction is an oxidation reaction.

ACIDS, BASES AND SALTS

Q1.  How the following substances will dissociate to produce ions in their solutions?

(i)    Hydrochloric acid

(ii)   Nitric Acid

(iii)  Sulphuric acid

(iv)  Sodium hydroxide

(v)   Potassium hydroxide

(vi)  Magnesium hydroxide             

Q2.  What is tooth enamel chemically? State the condition when it starts corroding. What happens when food particles left in the mouth after eating degrades? Why do doctors suggest use of tooth powder/ toothpaste to prevent tooth decay?

Q3. State  reason for the following:

(i)   Dry HCl gas does not change the colour of the dry blue litmus paper.

(ii) Alcohol and glucose also contain hydrogen but do not conduct electricity.

(iii)   Concentration of H3O+ ions is affected when a solution of an acid is diluted.

Q4.Explain the action of dilute hydrochloric acid on the following with chemical equation:

(i) Magnesium ribbon

(ii) Sodium Hydroxide

(iii) Crushed egg shells.

Q5.  (a) What is the action of litmus on:

                              (i) Dry ammonia gas

                              (ii) Solution of ammonia gas in water

  (b) State the observation you would make on adding sodium hydroxide to aqueous solution of:

                              (i)  Ferrous Sulphate

                              (ii) Aluminium chloride

               Give balanced chemical equation.

Q6. A few crystals of copper sulphate are heated in dry boiling tube:

(i) What is the colour before and after heating?

(ii) What is the reason for the colour change?

(iii) Can its original colour be restored? How?

Q7. A sanitary worker uses a white chemical having strong smell of chlorine gas to disinfect the water tank.

(i) Identify the chemical compound, write its chemical formula.

(ii) Give chemical equation for its preparation.

(iii) Write its two uses other than disinfection.

Q8. “Sodium hydrogen carbonate is a basic salt. “Justify the statement. How is it converted into washing soda? Explain. 

Q9. To an aqueous solution of sodium hydroxide, a few drops of phenolphthalein were added. What do you observe?  To this solution small amount of dil. HCI was added. What do you observe now? Explain your answer.

Q10.  Answer the following.

(a) Why is sodium hydrogen carbonate an essential ingredient in ant-acids?

(b) What happens, when crystals of washing soda are left open in dry air?

(c) Why does milkman add a small amount of baking soda to fresh milk?

Q11. (a) Why curd or sour substances should not be kept in brass and copper vessels?

            (b) Aqueous solution of HI shows acidic character, whereas aqueous solution of glucose does not. Why?

            (c) What will you observe when a small amount of copper oxide is added in a beaker containing dilute Hydrochloric Acid?

METALS AND NON-METALS 

Q1. Why Sodium forms Sodium Hydroxide when reacting with water whereas Aluminium forms only Aluminium Oxide?

Q2. What happens when:

(i)  ZnCO3   is heated in the absence of oxygen?

(ii)   a mixture of Cu2O and Cu2S is heated?

Q3.  Why the reduction process is always involved in the extraction of metals?

Q4. State the property utilised  in the following:

(i) Graphite in making electrodes.

(ii)  Electrical wires are coated with Polyvinyl Chloride (PVC) or a rubber-like material.

(iii) Metal alloys are used for making bells and strings of musical instruments.

Q5. A, B  and  C are  3 elements which  undergo chemical reactions   according   to    the following equations:

(a)  A2O3 + 2B → B2O3+ 2A

(b) 3CSO4 + 2B → B2 (SO4)3 + 3C

(c) 3CO + 2A → A2O3+ 3C              

Answer the following questions:

(i)  Which element is most reactive?

(ii)  Which element is least reactive?

(iii)  State the type of reaction listed above.

Q6. Compound P and aluminium are used to join railway tracks.

(i)  Identify the compound P.

(ii)   Name the reaction.

(iii)   Write the equation for it.

Q7. An ore on heating in air produces Sulphur Dioxide.

(i)  Which process would you suggest for its concentration?

(ii)   Describe briefly any two steps involved in the conversion of this concentrated ore into related metal.

Q8. State reason for the following:

(i) Non-metals cannot displace hydrogen from the acids.

(ii) Hydrogen is not a metal, yet it is placed in the activity series of metals.

(iii) Aluminium is more reactive than iron, yet its corrosion is less than that of iron.

Q9. (a)    List in tabular form any three chemical properties on the basis of which metals and non-metals are differentiated.

         (b) State two ways to prevent the rusting of iron.

Q10. Define alloys. List the properties of alloys that make them useful over pure metals? Explain this fact with suitable examples.

Q11. What is cinnabar? How is a metal extracted from cinnabar? Explain briefly.

Q12.Giving one example of each. Explain the method of obtaining the following metals from their compounds.

Metal ‘X’, which is low in the activity series.

Metal ‘Y’, which is in the middle in the activity series.

Metal ‘Z’, which is towards the top of the activity series.

Q13.  Write chemical equations for reactions taking place when

(a) Manganese Dioxide is heated with aluminium powder.

(b) Steam is passed over hot iron.

(c) Magnesium is treated with dil.HNO3 .

Q14. Give reasons for the following:

(a) Metals are regarded as electropositive elements.

 (b) When a piece of copper metal is added to a solution of zinc sulphate, no change takes place but the blue colour of copper sulphate fades away when a piece of zinc is placed in its solution.

(c) Articles made of aluminium do not corrode even though aluminium is an active metal.

Q15.  What is corrosion of metals? Name one metal which does not corrode and one which corrodes on being kept in open atmosphere.

Q16.   Zn is more electropositive than   Fe.  Therefore,  it should get corroded faster than  Fe. But it does not happen. Instead, it is used to galvanise  Iron.  Explain why?

Q17.       Why Al metal cannot be obtained by the reduction of Al2O3 with coke? Explain.

Q18.       List three properties of sodium in which it differs from the general physical properties of most of the metals.

CARBON AND ITS COMPOUNDS

Q1.   Compound  A has three carbon atoms,  which bums with non-sooty flame. Predict what is A? Write its electron dot structure.

Q2.    Give reasons for the following.

(i)  Ethanoic acid is used in the preservation of pickles.

(ii) CO2   is released on burning diamond as well as graphite.

Q3. An organic compound X of molecular formula C2H4O2 turns blue litmus to red and give brisk effervescence with Na2CO3 and NaHCO3. Identify X and name of the gas responsible for effervescence.

Q4.  Give answers to the following statements.

(i) An allotrope of carbon which has a two-dimensional layered structure consisting of fused benzene rings.

(ii)   An allotrope of carbon which looks like a soccer ball.

(iii)  An allotrope of carbon which contains both single and double bonds.      

Q5. Give the molecular formula and electron dot structure of ethyne and ethene.        

Q6. Define homologous series.  Examine it with an example.  Will there be any change in their physical properties? Give reason for your answer.                                        

Q7. What are soaps chemically? How do they differ from synthetic detergents? Also, mention their uses?

Q8. Give reason why carbon can neither form C4+ cations nor C4- anions , but forms covalent compounds. Also state the reason to explain why covalent compounds are bad conductors of electricity and have low melting and boiling points?

Q9. Draw the structures of the following compounds and   identify the   functional group present them:

(i) Butanoic acid

(ii) Bromopropane

(iii) Butyne

Q10. What is meant by homologous series of carbon compounds? Write the general formula of (i) alkenes, and  (ii)  alkynes. Draw the structures of the first member of each series to show the bonding between the two carbon atoms.

Q11. Write the name and general formula of a chain of hydrocarbons in which an addition reaction with hydrogen can take place. Stating the essential conditions required for an addition reaction to occur, write the chemical equation giving the name of the reactant and the product of such a reaction. 

Q12. Explain the following:

(i) CH3COOH is a weak acid.

(ii) Propene undergoes addition reaction.

(iii) The gas stoves have inlets for air.

Q13. Two carbon compounds X   and    Y   have the molecular formula C3H6 and C4H10 respectively. Which one of the two is most likely to show addition reaction? Justify your answer. Also give the chemical equation to explain the process of addition reaction in this case.

Q14. Explain why it is difficult to wash clothes with soap when water is hard. How do detergents help in overcoming this problem?

Q15. Write three different chemical reactions showing the conversion of ethanoic acid to sodium ethanoate. Write  balanced chemical equation in each  case.  Write the name of the reactants and the products other than ethanoic acid and sodium ethanoate in each case.

Q16. Write the name and molecular formula of an organic compound having its name suffixed with ‘ol’ and having two carbon atoms in its molecule. Write balanced chemical equation to indicate what happens when this compound is heated with excess  conc. H2SO4 and the name of main product formed. Also state the role of conc.  H2SO4 in the reaction.

Q17. Complete the following chemical equations :

Carbon compounds_1

 
 Q18. An organic compound ‘P’ is a constituent of wine. ‘P’ on reacting with acidified K2Cr207 forms another compound ‘Q’. When a piece of sodium is added to ‘Q’ a gas ‘R’ evolves which burns with a pop sound. Identify P, Q and  R and write the chemical equations of the reactions involved.
 

Q19. What are esters? How they are prepared? List two uses of esters.

Q20. How are the following products obtained from ethanol?

(i) Ethyl ethanoate

(ii) Sodium ethoxide.

Q21. An organic compound ‘N  of molecular formula C2H60 on oxidation  with dilute alkaline KMnO4 solution gives an acid ‘B’  with the same number of carbon atoms. Compound ‘A’  is often used for sterilization of skin by doctors.

(i) Name the compounds ‘A’ and ‘B’.

(ii) Write the chemical equation involved in the formation of B from A.

Q22. The molecules of alkene family are represented by a general formula, CnH2n.  Now answer the following.

(a) Wl1at is the name of alkene when n = 47

(b) What is the molecular formula of alkene, when n = 67

(c) What is the molecular formula and structural formula of the first member of the alkene family?

Q23. (a) Which among the following C2H6 , C2H5OH, CH3COOH is a hydrocarbon?

            (b) Differentiate between saturated and unsaturated hydrocarbons.  Give one example for each.

Q24. What is the role of metal or reagents written on arrows in the given chemical reactions?

Carbon compounds_2

Q25.  (i) Why does carbon form largest number of compounds? Give two reasons.            

             (ii)  Why are some of these called saturated and the other unsaturated compounds?

            (iii)  Which one of these two is more reactive and why?

CLASSIFICATION OF ELEMENTS

Q1.  Compare the radii of two species X and Y. Give reasons for your answer.  (i) X has 12 protons and 12 electrons  (ii) Y has 12 protons and 10 electrons. 

Q2. The atomic number of elements A, B, C, D and E are given below.

Element

A

B

C

D

E

Atomic Number

7

10

12

4

19

From the above table, answer the following questions.

(i)  Which two elements are chemically similar?

(ii)  Which element is an inert gas?

(iii)  Which element belongs to 3rd period of periodic table?

(iv) Which element among these is a non-metal?

Q3.  ‘Hydrogen occupies a  unique position in modern periodic table’, Justify the statement.           

Q4.  An element Y has a total of three shells, with six electrons in its valence shell.

(i) What will be the atomic number of this element?

(ii) In which period will you find this element?

(iii) Name another element which belongs to the same group as this element.

Q5.  Atomic radii of the elements of the second period are given below:

Period 2 elements

B

Be

O

N

Li

C

Atomic Radii (pm)

88

111

66

74

152

77

(i) Arrange the elements in the decreasing order of their atomic radii.

(ii) Identify the element that restively has :

            (a) largest radius          (b) smallest radius

(iii) Give reasons for the variation in atomic radii.

Q6.  From the part of a periodic table, answer the following questions:

1

Hydrogen

2

13

14

Carbon

15

16

Oxygen

17

Fluorine

X

  

P

  

Q

Y

     

R

Z

     

T

(i) Atomic number of oxygen is 8.  What would be the atomic number of fluorine?

(ii) Out of X and Q which element has larger atomic size? Give reason for your answer.

(iii) Out of Y and Z which element has smaller atomic size? Give reason for your answer.

Q7.  An element A reacts with oxygen to form A2O.

(i) State the number of electrons in the outermost orbit of A.

(ii) To which group of periodic table does A belong?

(iii) State whether A is a metal or non-metal.

Q8.  Two elements P and Q belong to the 3rd period of the modern periodic table and are in group 1 and group 2 respectively. Compare their following characteristics  in tabular form:

  • The number of electrons in their atoms
  • The sizes of their atoms
  • Their metallic character
  • Their tendencies to lose electrons
  • The formula of their oxides
  • The formula of their chlorides.

Q9. State the main aim of classifying elements. Which is the more fundamental property of elements that is used in the development of  Modern Periodic Table? Name and state the law based on this fundamental property.  On which side of the periodic table one can find metals, non-metals and metalloids?

Q10. An element ‘X’ with electronic configuration (2,8,2) combines separately with two radicals, (NO3 ) and (SO4)2−.

(i) Is ‘X’ a metal or a non-metal? Write the nature of its oxide.

(ii) Write the formula of the compounds of ‘X’ formed by the combination of these radicals. Are these compounds covalent or electrovalent?

Q11.  How   does   the  atomic   radius of  the  elements change on going

(i) from left to right in a period, and

(ii) down  a group

in the  Modern Periodic  Table  ?  Give reason in support of your answer.

Q12. What is meant by ‘group’ in the modern periodic table? How do the following change on moving from top to bottom in a group?

(i) Number of valence electrons

(ii) Number of occupied shells

(iii) Size of atoms

(iv) Metallic character of element

(v) Effective nuclear charge experienced by valence electrons.

Q13.  An element ‘X’ belongs to third period and  second group of the Modern Periodic Table.

(i) Write its electronic configuration.

(ii) Is it a metal  or non-metal? Why?

(iii) Write the formula of the compound formed when ‘X’ reacts with an element.

                   (a) Y of electronic configuration 2, 6 and 

                   (b) z with electronic configuration 2, 8, 7.

Q14. An element ‘X’ belongs to 3rd period and group 16 of the Modern Periodic Table.

(i) Determine the number of valence electrons and the valency of ‘X’.

(ii) Molecular formula of the compound when ‘X’ reacts with hydrogen and write its electron dot structure.

(iii) Name the element ‘X’  and state whether it is metallic or non-metallic.

Q15. Two elements X  and  Y belong to group  1 and  2 respectively in the same period of the periodic table. Compare  these elements with respect to :

(i) number of electrons in their outermost orbit

(ii) their valencies

(iii) metallic character

(iv) their atomic size

(v) formula  of their chlorides

(vii) formula  of their sulphates.

Q16. Given  below  are  some  elements of the modern periodic  table :

4Be, 9F, 14Si, 19K, 20Ca.

(i) Select the element that has one electron in the outermost shell and write its electronic configuration.

(ii) Select two elements that belong to the same group. give reason for your answer.

(iii) Select two elements that belong to the same period. Which one of the two has bigger atomic size?

Q17.  State the difference between modern periodic table and Mendeleev’s periodic table.

Q18. (a) Can the following groups of elements be classified as Dobereiner’s triad?

                        (i). Na, Si, Cl        (ii) Be, Mg, Ca

Explain by giving reason.

(Atomic mass of Be 9; Na 23; Mg 24; Si 28; Cl 35; Ca 40)

         (b) Upto which element, the law of octaves was found to be applicable?

Q19.       Four elements A, B, C and D have atomic numbers 12, 13, 14 and  15 respectively. Answer the following questions giving reasons.

(i)  What is the valency of B?

(ii)  Classify these elements as metals and non-metals.

(iii)  Which· of these elements will form the most basic oxide?

Q20.       X is an element of modern periodic table. It is surrounded by elements having atomic number  17, 34, 36 and  53.

(i)   What is the atomic number of X?

(ii)   Predict its position in the periodic table.

(iii) Which among these do not belong to the same Group?

***

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