Chemical reactions and equations -important questions with answer

MULTIPLE CHOICE QUESTIONS

1.        Barium chloride on reacting with ammonium sulphate forms barium sulphate and ammonium chloride. Which of the following correctly represents the type of the reaction involved?

         (a) Displacement reaction

          (b) Decomposition reaction

          (c )    Combination reaction

          (d)  Double displacement reaction

2. Chemically rust is

  (a)  ferric sulphate

            (b)  ferric oxide 

           (c)hydrated ferrous oxide

          (d) hydrated ferric oxide

 3.    When green colour ferrous sulphate crystals are heated, its colour changes as

                 (a)  it is decomposed to ferric oxide

                       (b)  it loses water of crystallisation

                        (c)  it forms SO2

                        (d)  it forms SO3

            FILL IN THE BLANKS

           4.        Precipitation reactions are type of         

            5.        Decomposition of calcium carbonate forms and .

            6.        Magnesium ribbon is rubbed with sand paper to remove .

          ONE MARK QUESTIONS

            7.        Name the gas produced by the action of dilute hydrochloric acid on zinc granule.

                8.        Which gas is used to prevent rancidity in potato chips packets?

                9.        Write one equation to represent thermal decomposition.

            ASSERTIONS AND REASON

              For the question numbers 10, 11 and 12, two statements are given- one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:

                (a) Both A and R are true and R is the correct explanation of A.

                (b) Both A and R are true but R is not the correct explanation of A.

                (c) A is true but R is false.

                (d) A is false but R is true.

            1.        Assertion: Colour of copper sulphate solution does not change when the iron nail is kept in it.                Reason: Iron is more reactive than copper and displaces it.

            2.        Assertion: Combustion reaction is also called an exothermic oxidation reaction.                                       Reason:   In this reaction oxygen is added and heat energy is released.

            3.        Assertion: Pungent smelling gas is produced when sulphur burns in air. Reason: Sulphur dioxide is formed on the reaction of sulphur with oxygen.

FIVE MARK QUESTIONS

1.         (a) Barium chloride reacts with aluminium sulphate to give aluminium chloride and barium sulphate.

(i)  State the type of reaction.

(ii)  Translate the above statement into a balanced chemical equation.

(b) A metal ‘X’ acquires a green colour coating on its surface on exposure to air.

(i)  Identify the metal ‘X’ and name the process responsible for this change.

(ii)  Name and write the chemical formula of the green colour coating formed on the surface of the metal.

2.         2g of Ferrous Sulphate crystals are heated in a boiling tube.

(i)  State 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.

(b) Describe an activity to show a decomposition reaction in which light is used to decompose a reactant. Write the chemical equation of the reaction and state one of its uses.

3.         (a)Why is it essential to balance a chemical equation?

(b) With the help of a chemical reaction, explain the decomposition of lead nitrate. 

(c)Can rusting of iron take place in distilled water? Give a reason.

(d)  Give two methods to prevent rancidity.

(e)   How will you test for the gas which is liberated when HCl reacts with an active metal?

4.         CASE- STUDY

Answer question numbers 20 (a) to 20 (d) based on your understanding of the following paragraph and the related studied concepts.

A strip of metal X is immersed in the aqueous solution  of salt  YSO4.  After some time a layer  of metal Y  from the salt solution is deposited on the strip of X. Whereas the metal X is used    for galvanisation and metal Y is used in electrical cables.

(a) Identify the metal X. (b)What could be the metal Y? (c)Can you name the salt YSO4?

(d)Represent the above change in the form of a chemical equation.

General Trends of different properties in the periods and groups

General Trends of different properties in the periods and groups                                           

 

Chemistry Revision test paper- 1

 CLASS-XI        SUBJECT-   CHEMISTRY 

TIME ALLOTTED: 3 hrs            Max. Marks: 70

General Instructions:

1.      AII the questions are compulsory. There are 33 questions in this paper.

2.      Q .1 and Q 2. Are case based questions and have 4 parts each.

3.      Q3 to Q 11. Are MCQs and carry one mark each

4.      Q 12 to Q16. Are Assertion –Reason questions and carry one mark each.

5.      Q17 to Q 25 are short answer questions and carry two marks each.

6.      Q 26 TO 30  are also short answer questions  and carry three marks each

7.      Q 31 to 33 are long answer questions and carry five marks each

Q1.Case study 1

    An electron in an atom can be completely designated with the help of four quantum numbers. Out of these, the first three i.e; Principal (n), Azimuthal (l) and Magnetic (m) quantum numbers are obtained from the  solution of Schrodinger wave equation while spin quantum (s) arise from the spin of the electron around its axis whether clockwise or anti clockwise. Out of these, principal quantum number tells about the size, Azimuthal quantum number about the shape while Magnetic quantum number signifies the orientation of the electron orbital.  

A. The electronic configuration number of P in H₃ PO₄

    (a)   1s² 2s²  2p⁶ 3s² 3p³

    (b)   1s² 2s² 2p⁶ 3s²

    (c)    1s² 2s² 2p⁶

    (d)   1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹

    B. How many electrons in a given atom have the following set of quantum numbers?

 n = 3, l = 2, m = +2, s = -1/2

   (a)   1

    (b)   18

    (c)    14

    (d)   Not possible

                        OR

.   In an atom, the total number of electron having quantum numbers  n = 4; m_l =1 and  m_s = -1/2 is:

   (a)   3

    (b)   4

    (c)    6

    (d)   8

    C. Correct set of four quantum numbers for the valence electron of rubidium ( Z = 37) is :

    (a)    5, 0, 0,  + 1/2

    (b)   5,1,0, +1/2

    (c)    5, 1, 1, +1/2

    (d)   6, 0,0,+ ½

    D. The electrons identified by quantum numbers n and l

    (i)                n =4, l = 1

    (ii)               n =4, l =0

    (iii)             n =3, l =2   

    (iv)             n =3, l =1

    can be placed in order of increasing energy from the lowest to the highest as:

(a)   (iv)<(ii)<(iii)<(i)

(b)   (ii)<(iv)<(i)<(iii)

(c)    (i)<(iii)<(ii)<(iv)

(d)   (iii)<(i)<(iv)<(ii)

Q 2.  Case Study- II

The concept of hybridisation has been introduced to explain the shapes of molecules. It involves  the intermixing of two or more atomic orbitals belonging to same atom   but in different sub –shells so as to intermix and redistribute energies to form equivalent orbitals called hybrid orbitals. Depending upon the number and nature of the orbitals involved, the hybridisation may be divided into sp (linear), sp² (trigonal), sp³ ( tetrahedral), sp³d³ (pentagonal bipyramidal) types. It may be noted that the orbitals of isolated atoms never hybridise and they do so at the time of bond formation.

    (a)   If both assertion and reason are correct and reason is correct explanation for assertion

    (b)   If both assertion and reason are correct but reason is not correct explanation for assertion

    (c)    If assertion is correct but reason is incorrect

    (d)   If both assertion and reason are incorrect

     A.     Assertion : SF₆ molecule has octahedral geometry

         Reason: Sulphur atom in SF₆  molecule is in sp³ d hybridisation state.

    B.      Assertion: All F---S---F bonds  in SF₄   are greater than 90⁰   but less than 180⁰  

  Reason:  The lone pair –bond pair  repulsion is weaker than bond pair – bond pair repulsion

     C.      Assertion: If the central atom in a  covalent molecule is  surrounded only by shared electron pairs, the molecule has a regular geometry.

Reason : The force of repulsion in all the shared electron pairs are equivalent and  these are equidistant from the central atom.

                                                    OR

Assertion: There are  ten valence electrons on the sulphur atom in SF₄  MOLECULE.

 Reason: The structure of SF₄  molecule is distorted trigonal  bipyramidal.

     D.     Assertion: CIF₃  has T-shape structure.

Reason: it has two lone pairs arranged at angle of 180⁰    

Q3Whichofthefollowinghasneither secondary nor tertiary  hydrogen .?

 (a)   Isobutane    (b) Isopentane  (c) Pentane  (d) Neopentane

Q4. The addition of carbonyl compound to HCN is an example of (a ) Nucleophilic substitution (b) Electrophilic addition (c) Nucleophilic addition (d) Electrophilic substitution

Q5. In which of the following  homolytic  bond fission takes place (a)Alkaline hydrolysis of C₂H₅Cl (b) addition of HBr to double bond  (c) photochlorination of methane (d) Nitration of of Benzene.

OR

The principal functional group from the following is----

(a)   –CHO     (b)  -COOH  (c) –CONH₂ (d) –COCl

Q6. Pick  the electrophiles from the following   NH ₃ ,NO₂⁺ ,CN^- ,SO₃ ,ROH,FeCI₃

(a)   NO₂⁺ ,SO₃ , FeCI₃

(b)   ROH,NH₃ ,CN^-

(c)    FeCI₃ ,ROH,SO₃

(d)   ROH,CN^- ,SO₃

                     OR

In which of the following functional groups isomerism is not possible

(a)Alcohols

(b) Aldehydes

( c) Alkyl halides

(d)Cyanides

Q7. The state of hybridisation of carbocation  is---

(a)   s p

(b)    s p²

(c)    sp³

(d)   sp3 d

                                   OR

What is the correct order of decreasing stability of the following carbocations

1.CH_{3 ----}C⁺ H----CH₃      2. CH₃---C⁺ H---OCH₃   3. CH₃---C⁺ H—CH₂---OCH₃

(a) 2>1>3

(b) 2>3>1

( c )3>1>2

(d ) 1>3>2

Q 8 . For the reaction PCI₃ (g) +CI₂(g)<--àP CI ₅(g). The value of K_c at 250⁰ C is 26 mol L^-1..The  value of K_p at the same temperature will be

(a)   0.61 atm^-1

(b)   O.57 atm^-1

(c)    0.83 atm^-1

(d)   0.46 atm^-1

Q9. The Ph of a 0.1 M  Solution of acid HA  is 3.The  value of ionization constant K_a of this acid is  

(a) 1x 10^-3      (b) 1x10^-5    (c) 1x10^-7   (d) 3x10^-1

Q10. The concentration of Hydrogen ion in a sample of soft drink is 3.8 x10^-3 M. The p H of the solution is (a) 3.84  (b)  2.42  (c)4.44   (d)  1.42

Q11 . The equilibrium constant for the reaction N₂ + O₂ -à2NO at temperature T  is 4x10^-4 .The value of equilibrium constant for the reaction NO à1/2N₂ +1/2 O₂  at the same temperature is------   (a) 0.0025  (b) .004  (c ) 50  (d) 0.02

                                                    OR

The solubility product of Silver bromide is 7.7 x10^-13 mol² L^-2. The solubility of salt will be----

(a)8.77x10^-7 mol l^-1     (b) 0.089 mol l^-1    (c) 3.7 mol L^-1   (d) 0.0077 mol L^-1 

Q  No. 12 to 16 are Assertion and Reason  questions for which the correct option has to be selected from the following:

(A)   Both Assertion and Reason are  correct statements  and Reason is correct explanation of Assertion

(B)  Both Assertion and Reason are correct statements but Reason is not correct explanation of Assertion

(C )Assertion is correct but Reason is not correct

(D) Assertion is not correct but Reason is correct

(E) Assertion is not correct Reason is also not correct

Q12. Assertion: One mole of NaCl  contains 6.022x10²³ formula units of Sodium chloride

Reason: 58.5 g of NaCI also contains 6.022x10²³  formula units of Sodium chloride

Q13. Assertion: Molarity and Molality both depend only upon the number of moles of solute particles

Reason : Molarity of a solution does not depend upon temperature whereas molality depends

Q14.Assertion: Many endothermic reactions that are nonspontaneous at room temperature become spontaneous at high temperature

Reason: Entropy of the system increases with rise in temperature

Q15. Assertion: Enthalpy of formation of HCI  is equal to bond energy of HCI

Reason: Enthalpy of formation and bond energy both involve the formation of one mole of HCI  from the elements

Q16.Assertion: Zinc displaces Copper from Copper sulphate solution

Reason: Cu  is more reactive than Zn

                                                        OR

Assertion: Oxidation state of Hydrogen is +1 in  H₂ O and -1 in CaH₂

Reason: CaH₂  is a metal hydride

Q17. Benzyl   carbocation  is  more stable than ethyl carbocation. Justify  by resonating structures

Q18.  Write structures of various carbocations  that can be obtained from 2-Methyl  butane. Arrange these carbocations in increasing order of stability  with reason.

                                                    OR

(a)Give  bond  line  formula  for  2,2,4-Trimethylpentane  and write IUPAC name of  Iso-propyl methyl ketone.

(b)What is the hybridisation of  each carbon in H₂ C=C=CH₂ .

Q19. Determine the degree of ionisation and p H of a 0.05 M ammonia solution .Also calculate ionisation  constant of the conjugate acid of ammonia, given that K_b  for NH₃ is 1.77 x 10^-5.

Q 20.  20 ml of 1.5x10^-5  M BaCl₂ solution is mixed with 40ml of 0.9x10^-5 M Na₂SO₄ solution. Will a precipitate get formed? (solubility product for BaSO₄ =1x10^-10).

Q 21.  Give reasons:

(a)   Lakes freeze from top towards bottom

(b)    Do you expect the carbon hydrides of the type  (C_n H_2n+2  )to act as Lewis acid or base ?Justify  your answer.

Q 22.  Explain electron deficient and electron rich molecular hydrides with examples.

                                                            OR

    (1)   Is   it correct to say that hydrogen can behave as a metal? State the condition  under which such behaviour is possible.

    (2)   Temporary hard water becomes soft on heating. Explain by giving chemical equation.

Q 23. Give reasons:

    (1)   Mg²⁺ is much more heavily hydrated than Na^+. Why ?

    (2)   Why are halides of beryllium polymeric?

Q 24.  (1)   Arrange the alkaline earth metal carbonates in the decreasing order of thermal stability.

           (2)    L_iI is more soluble than KI in ethanol. Comment on this statement.

Q 25.  _{Explain the following}                              

   _{(a)       Galium has higher  ionisation enthalpy than aluminium,}

   _{(b)      Aluminium forms ( AlF6)}^3- _{ion but Boron does not form( BF6)}^3-  _ion.

                                          _OR

   _{(a)        Explain the following}

   CCl₄ is immiscible in water where as SiCl₄  is easily hydrolysed,

     (b)   Select the member of group 14 that

         (i)     Forms the most acidic dioxide,

  (II) Is commonly found in +2 oxidation state.

Q  26.  1.0 g of a mixture of carbonates of calcium and magnesium gave 240cm³ of  CO₂  at S.T.P. Calculate percentage composition of the mixture.

Q 27. (a)   Calculate the kinetic energy of O₂ molecule which has wave length of 2.5  pm.

(b)   With what velocity must an electron travel so that its momentum is equal to that of a photon of wave length = 5200A⁰. ?

Q 28. (a)   Compare the relative stabilities of  O₂^2- and N₂^2- and comment on their magnetic behaviour,

(b)   H₂O molecule is a triatomic molecule but its geometry is not linear, why?

Q 29.  Calculate the degree of ionisation of 0.05M acetic acid if its pka value is 4.74. How is degree of dissociation affected when the solution contains ( a) 0.01M HCl  (b) 0.1M HCl

                   OR

Calculate the degree of ionization of 0.02M acetic acid if its  Ka = 1,8x10^-5. What would  be the degree of ionization if the solution also contains 0.01M sodium acetate.

Q 30. (a) Balance the following reaction by half equation method ,in basic medium

 MnO₄^- (aq) + I^- (aq)  à MnO₂ (S) + I₂ (S)

(b)Is the reaction BaO₂+ H₂SO₄ à Ba SO₄ + H₂ O₂ is a redox reaction.

                                OR

(a)   Balance the following reaction by half reaction method in acidic medium

                 Cr₂O₇^2- + Fe^{2 +} ---à Cr³⁺ + Fe³⁺ + H₂O

    (b)   Identify oxidising and reducing agents in the following  reaction

        3CuO + 2NH₃  à 3Cu +N₂ +2H₂ O

    Q31. Comment on the  following  observations.

    (a)   F₂  is  more   reactive  than  CI₂.

    (b)   The  formation  of  F^-1 (g)  from F (g) is exothermic whereas that of O^2- (g) from O (g) is endothermic. Explain.

    (c)    Alkali metals do not form positive ions, why?

    (d)   Third period has eight and not eighteen elements.

    (e)   Second ionization enthalpy is always higher than first ionization enthalpy.

                                           OR

Answer the following questions.

(1)   Which two elements in the periodic table would you expect to combine in the most violent fashion.

(a)   Cs and F     (b)  Cl and F

(2)   Write IUPAC name for the element with atomic number 121.

(3)   Which of the following has maximum number of unpaired electrons

      (a) Mg²⁺   (b) Ti³⁺    (c)  V³⁺    (d)   Fe²⁺

(4)  Write general electronic configuration of d- block elements,

(5) Mg²⁺  ion is smaller than O^2-  ion although both have same electronic configuration

Q32 (a) What volume of air containing 20% of oxygen by volume is required to completely burn 1kg of sulphur (S₈ ) which contain 4% material which does not burn . . Sulphur burns according  to the reaction  1/8 S₈ +O₂ ---àSO₂ 

(b)     When 5.0L of butane  are burnt in excess of oxygen at  67⁰  C and 2 bar pressure .Calculate  the volume of CO₂ evolved.

(c)    If the value of “A” for a gas is zero, can it be liquefied.

                                                  OR

 (a). Two gases A &B having molecular mases 60 and 45 respectively are enclosed in a vessel. The mass of A is 0.50g and that of B is 0.20g. The total pressure of the mixture is 0.921 bar. Calculate the partial pressure of two gases.

(b) Aluminium reacts with sodium hydroxide to produce sodium meta aluminate and hydrogen. What volume of hydrogen  at 20⁰ C and one bar will be released when 0.15gof aluminium reacts?

(c) Out of CO₂ and  NH₃  gases, which is expected  to show more deviation from ideal gas behaviour.

Q.33. (a) Calculate the equilibrium constant for the following reaction at 298k and 1 atm pressure:

NO (g) + 1/2O₂  (g) ßàNO₂ (g)

Given standard enthalpy change of formation of NO (g) is = 90.4 kJ ^mol-1, NO₂ (g)          =33.8 KJ nJ^1,, Standard entropy change at 298 K is -70.8JK^-1.

(b)Using the data provided, calculate the multiple bond energy (KJ mol^-1 ) in C₂H₂  ( The bond energy of C-H bond is 350 KJmol^-1 )

2C(S)+ H₂ (g)-àC₂ H₂ (g)  Change in enthalpy =225KJ mol^-1

2C(S)----à 2 C (g)  , change in enthalpy= 1410KJ mol^-1

H₂ (g) --à 2H (g)  , change in enthalpy = 330 mol^-1

                                                  OR

(a)  Calculate the free  energy change on dissolving one mole  of NaCl at  25⁰C. Lattice energy = 777.8KJ mol^-1 , hydration energy=-774 KJ mol^-1 of NaCl , Entropy change at 25⁰ C =0.043 KJ mol ^-1

(b) For the evaporation process , H₂  O(l) ß-àH₂ O(g), change in enthalpy=44KJ  and change in entropy=118.8x10^-3 KJ k^-1  .Calculate the temperature at which water vapours and  water are in equilibrium.

(c)     For a reaction M₂O (S)--à 2 M(S) + 1/2O₂ (g),  change in enthalpy =30 KJ and change in entropy =0.07KJK^-1 at 1 atm. Calculate up to which temp.the reaction would not be spontaneous.  

 

 Answer key  is coming soon