1 MARK QUESTIONS for Class 10 CHEMISTRY

CHEMICAL REACTIONS AND EQUATIONS

Q1.  In the reaction,

Be2C + xH2O  → yBe(OH)2 +CH4

write the values of x and y.

Q2.  Name the brown coloured gas evolved when lead nitrate crystals are heated in a dry test tube.

Q3. What is the difference between the following two reactions?

(i)  Mg + 2HC1 → MgCl2  + H2

(ii)   NaOH + HCl → NaCl + H2O

Q4. Double displacement reactions are also known as precipitation reactions. Why?

Q5. State one basic difference between a physical change and a chemical change.

Q6. Why is hydrogen peroxide kept in coloured bottles?

Q7.  Zinc liberates hydrogen gas when reacts with dilute Hydrochloric Acid, whereas copper does not. Write the reason?

Q8. Aluminium is a reactive metal. But is still used for packing food articles. Write one reason for its use?

Directions (Q. Nos.  09-13)  In the following questions a statement of Assertion is

followed by a statement of Reason. Mark the correct choice as

(a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.

(b) If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.

(c) If Assertion is true but Reason is false.

(d) If Reason is true but Assertion ls false.

(e) If both Assertion and Reason are false.

Q9. Assertion:   Chemical reaction changes the physical and chemical state of  a substance.

      Reason:  When electric current is passed through water (liquid),  it decomposes to produce hydrogen and oxygen gases.

Q10. Assertion: In a balanced chemical equation, total mass of the each element towards reactant side= total mass of the same element towards product side.

Reason: Mass can neither be created nor destroyed during a chemical change.

Q11. Assertion: When calcium carbonate is heated, it decomposes to give calcium oxide and carbon dioxide.

Reason: The decomposition reaction takes place on application of heat, therefore, its and endothermic reaction.

Q12. Assertion: Chips manufacturers usually flush bags of chips with gas such as nitrogen to prevent the chips from getting oxidised.

Reason: This increase the taste of the chips and helps in their digestion.

Q13. Assertion: Rusting of iron metal is the most common form of corrosion.

Reason: The effect of rusting of iron can be reversed if they are left open in sunlight.

Q14. Name and state the law which is kept in mind while we balance a chemical equation.

(a) Law of Equal Proportion                          

(b) Law of Conservation of Mass

(c) Daltons Law                                                 

(d) Avogadro’s Law

Q15. What is breaking and making of bonds in chemical reaction called?

(a) Chemical Reaction                     

(b) Chemical Equation

(c) Chemical Bonding                     

(d) Chemical Equilibrium

Q16. A red-brown gas is released along with O2 and lead oxide on heating lead nitrate. It is an example of

(a) combination  reaction                 

(b) oxidation reaction

(c) decomposition reaction              

(d) reduction reaction

Q17. What are the coefficients of the correctly balanced equation?

?Fe2O3 + ?CO → ?Fe+ ?CO2

(a)0, 2, 2,3           

(b) 1,3,2,3           

(c)1,2,2,2            

(d)2,6, 4,3

Q18· Burning of a candle is a

(a) physical change           

(b) a chemical change

(c) slow change                 

(d) gaseous change

ACIDS, BASES AND SALTS

Q1. What is the pH of gastric juice,  which is released during  digestion?

Q2. A student has four samples  A, B, C, D containing dil. HCI, aqueous KCI, dil. NaOH and distilled water respectively. Which two samples would show an equal value of pH?

Q3. How does a strong acid differ from a concentrated acid?

Q4. Name three chemicals in which common salt used  as the raw material.

Q5. Which gas would be evolved, if sodium bicarbonate is treated with tartaric acid?

Q6. Name two crystalline substances which do not contain water of crystallisation.

Q7. Name the acid present in ant sting.

Q8. Which gas is usually liberated when an acid reacts with a metal?

Q9. Why does tooth decay start when the pH of mouth is lower than 5.5?

Q10. Name a salt which does not contain water of crystallisation.

Q11. Why is tartaric acid added into baking soda to get baking powder?

Q12. How does the concentration of H3O+ ions get affected, when a solution of an acid is diluted?

Q13. Why does dry HCI not change the colour of dry litmus?

Q14.  What happens when nitric acid is added to an eggshell?

Directions (Q. Nos. 15-19)  In the following questions a statement of Assertion is followed by a statement of Reason. Mark the correct choice as

(a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.               ·

(b) If both Assertion and Reason are true but Reason is not the correct -explanation of Assertion.

(c) If Assertion is true but Reason is false.

(d) If Reason is true but Assertion is false.

(e). If both Assertion and Reason are false.

Q15. Assertion: Acetic acid does not act as an acid in benzene solution.

            Reason: Benzene is non-polar.

Q16. Assertion: Calcium oxide is a base but not an alkali.

           Reason: Calcium oxide is insoluble in water.

Q17. Assertion: There is no change in the colour of litmus paper when brought in contact with distilled water.

            Reason: Litmus Paper is used to find whether an solution is Acidic or Basic.

Q18. Assertion: When bleaching power is left in the open, its colour changes from blue to white.

            Reason: The change in colour as oxygen breaks away from the compound.

Q19. Assertion: Sodium and Potassium is kept inside kerosene.

           Reason: Sodium does not react with organic solvents like kerosene.

Q20. What is the common name of CaOCl2 ?

(a) Bleaching powder       

(b) Baking soda

(c) Washing soda              

(d) Lime water

Q21.  Which one will turn red litmus blue?

(a) Vinegar                        

(b) Lemon juice

(c) Soft drinks                   

(d) Baking soda solution

Q22.  Among sulphurous acid and sulphuric acid, which is stronger?

(a) Sulphurous acid is stronger than Sulphuric Acid

(b) Sulphuric Acid is stronger than Sulphurous acid.

(c ) Sulphuric Acid and Sulphurous acid are equal in strength.

(d) Dilute Sulphuric Acid is stronger than dilute Sulphurous acid.

METALS AND NON-METALS

Q1.  Name two metals which react with dil.HNO3 to evolve hydrogen gas.

Q2.  Name one metal which forms an amphoteric oxide.

Q3.  Name a solvent in which electrovalent compounds are soluble and a solvent in which they are not.

Q4. Show the formation of MgO by the transfer of electrons in the two elements using electron  dot structures.

Q5. Why does calcium float in water?

Q6. Name any two alloys whose electrical conductivity is less than that of pure metals.

Q7. Name one metal and one non-metal which exists in liquid state at room temperature.

Q8. Make a distinction between metals and non-metals with respect to the nature of their oxide.

Q9. Why is carbon not used for reducing aluminium from aluminium oxide?

Q10.  Why ionic compounds do not conduct electricity in solid state although they are made up of ions?

Q11.  Which of the following elements is a metal?

Metals Non Metals_1

Q12.       For the reduction of metal oxide to metal,  suggest a reducing agent cheaper than aluminium.

Directions (Q.  Nos.  13-17)  In the following questions a statement of Assertion is followed by a statement of Reason. Mark the correct choice as

(a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.

(b) If both Assertion and Reason are true but Reason ·is not the correct explanation of Assertion.

(c) If Assertion is true but Reason is false.

(d) If Reason is true but Assertion is false.

(e) If both Assertion and Reason are false.

  1. Assertion: Iron can be obtained from Fe2O3 by reduction with aluminium.

               Reason: The process is known as thermite process.

  1. Assertion: Elements Pt, Ag, noble gases, etc. occur in native state in nature.

               Reason: Elements which are attacked by moisture, oxygen and CO2  of air occur in native state.

  1. Assertion: Reactivity Series is an arrangement of element based on their reactivity.

               Reason: Reactivity Series is used to separate elements based on their reactivity.

  1. Assertion: Bauxite is the most important ore of Aluminium.

               Reason: Carbon is used to reduce bauxite to aluminium.

  1. Assertion: Brass is an alloy of Zinc and Magnesium.

               Reason: Alloys are homogenous mixture of two or more metals.

Q18. Select odd one out from the following elements.

(a) Bismut           

(b) Copper          

(c) Zinc

(d) Arsenic

Q19.  Which element is present at the top of the reactivity series and is stored in kerosene oil?

(a) Potassium           

(b) Tin                     

(c) Lead               

(d) Gold

CARBON AND ITS COMPOUNDS

Q1. “Carbon tetrachloride is not a good conductor of electricity”. Justify?

Q2. Why is fullerene so called?

Q3. What is the composition of natural gas used for cooking?

Q4.  What do you mean by the term soapless soaps?

Q5. What is the disadvantage of detergents over soaps?

Q6. Molecular formula of a hydrocarbon is C3H8   Write is name and draw its complete structure.

Q7. Write the name and structure of an alcohol with three carbon atoms in its molecule.

Q8. Name the functional group present in CH3COCH3 and state the name of this compound.

Q9. Why are mineral acids stronger acids than carboxylic acids?

Q10. Why do alkanes burn with blue or clean flame?

Q11.   How two successive members of a homologous series differ from each other?

Q12.   Graphite is a covalent molecule but a good conductor of electricity. Why?

Directions (Q. Nos.  13- 17)  In the following questions a statement of Assertion is

followed by a statement of Reason. Mark the correct choice as:          

(a) If both  Assertion and Reason are true and Reason is the correct explanation of Assertion.

(b)  If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.

(c)  If Assertion is true but Reason is false.

(d)  If Reason is true but Assertion is false.

(e) If both  Assertion and Reason are false.

Q13. Assertion: Branched-chain alkanes have lower boiling points.

            Reason: As molecular size decreases, boiling point increases.

Q14. Assertion: Olefins have the general formula  CnH2n

            Reason: There is one triple bond between two carbon atoms in their molecules.

Q15.  Assertion: Denatured alcohol is Ethyl Alcohol when mixed with Methanol

             Reason: Denaturing of alcohol prevents misuse of alcohol meant for Industrial use.

Q16.  Assertion: Acetic Acid is an inorganic solvent.

             Reason: Inorganic chemicals are soluble in Acetic Acid.

Q17.  Assertion: Cleaning action of soaps is due to formation of miscelles.

             Reason: Miscelles are formed when hydrophilic part of the soap molecule

Q14. When you add a few drops of acetic acid to a test-tube containing sodium bicarbonate powder, which one of the following is your observation?

(a ) No reaction takes place.

(b) A  colourless gas with pungent smell is released with brisk effervescence.

(c) A  brown coloured gas is released with brisk effervescence.

Q15. Choose the correct general formula of alkane.

(a) CnH2n-2           

(b) C2nH2n+2

(c) CnH2n       

(d) CnH2n+2

Q16. According to given figure,  how many electrons are being shared by each oxygen.

(a) 2        

(b) 3                          

(c)  1                 

(d) 4

CLASSIFICATION OF ELEMENTS

Q1. Upto which element, the  Law of Octaves was found to be applicable?

Q2. Why are noble gases missing from Newlands’ Octaves?

Q3. Atomic number is considered to be a more appropriate parameter than atomic mass for classification of elements in a periodic table. Why?

Q4. Out of Na, Al, Si, P which element exhibits maximum number of valence electrons?

Q5. Elements  A,   B,  C  and   D  have atomic numbers  1,  8,   11  and    19  respectively. Choose the odd element and give reason for your answer. 

Q6. Write the correct increasing order of the atomic radii of O, F and N.

Q7. Which group of elements will form an acidic oxide?

Q8. An element X is in  second period of group 16 of the periodic table. Is it metal or non-metal? Give reason for your answer.

Q9. Write two reasons responsible for late discovery of noble gases. 

Q10. Why hydrogen should be placed in Group I?

Q11. State one reason for placing  Mg and   Ca in the same group of the periodic table.

Q12. The atomic numbers of three elements A, B and C are 12, 18 and 20 respectively. State giving reason, which two elements will show similar properties.

Q13. The atomic number of three-element X, Y and  Z are 3, 11 and 17 respectively. State giving reason which two elements will show similar chemical properties.

Q14. How does the electronegativity changes as we move from left to right across a period?

Q15.  What is meant by periodicity in properties of elements with reference to periodic table?

Q16. Why is lithium atom smaller than potassium atom?

Q17. What is the basis for the classification of modern periodic table?

Q18. Name the two elements whose valencies are equal to their group number.

Q19. Why does silicon has valency  4 and chlorine  1?

Directions (Q. Nos. 10 – 14)  In the following questions a statement of Assertion is followed by a statement of Reason. Mark the correct choice as:

(a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.

(b) If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.            ·

(c) If Assertion is true but Reason is false.

(d) If Reason is true but Assertion is false.

(e) If both Assertion and Reason are false.

Q10. Assertion: Atomic size of potassium is greater than that of sodium.

           Reason: As we go down the group, atomic radius increases.

Q11. Assertion: Alkali metals have smallest size in a period.

            Reason: They are at the extreme left of the periodic table.

Q12. Assertion: Nobel Elements were not included by Mendeleev’s Periodic Table.

            Reason: Mendeleev did not know where to place in his Periodic Table.

Q13. Assertion: Electronegativity decreases from left to right along a period in the Modern Periodic Table.

            Reason: As electron is added to the same shell when moving from left to right along a period, the force of attraction increases between the nucleus and the electron on the last shell.

Q14. Assertion: Atomic Mass of certain elements are expressed in fraction taking in account the availability of its various isotopes.

            Reason: Isotopes of an element have the same atomic mass but different atomic number.

Q15. When you add a few drops of acetic acid to a test-tube containing sodium bicarbonate powder, which one of the following is your observation?

(a ) No reaction takes place.

(b) A  colourless gas with pungent smell is released with brisk effervescence.

(c) A  brown coloured gas is released with brisk effervescence.

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