Solved question paper for CHEM May-2019 (DIPLOMA Mechanical Engineering (RAC) 1st-2nd)

Question paper 1

1. SECTION-A

   Q1. Do as directed.         10x1.5=15

   a. The nuclease of an atom contains _____and_____

   Answer:

   Protons and neutrons

2. b. Reducing agents ______Electrons

   Answer:

   Transfer

3. c. L shell has ________ sub shells.

   Answer:

   Two

4. d. Neutron was discovered by__________

   Answer:

   James Chadwick

6. e. Chemical name of permutit is _________

   Answer:

   Sodium aluminium silicate or zeolite

7. f. Units of molarity are____________.

   Answer:

   M

8. g. Cations are _________charged ions.

   Answer:

   Positively

9. h. The functional group of Ketone is____________

   Answer:

   R-C-R

11. i. Isotopes have same number of protons (T/F)

    Answer:

    True

12. j. A solution of three components is a binary solution. (T/F)

    Answer:

    False

13. SECTION-B

    Q2. Attempt any six questions.       6x5=30

    i. What are the limitations of a chemical equation?

    Answer:

    1. It doesn’t tell us whether a reaction can proceed completly or not.

    2.Chemical equation doesn’t tell us the speed of reaction.

    3. It doesn’t tell us about the physical changes like color, state etc.

    4. It tells us about through which method the reaction proceeds.

14. ii. Differentiate between an orbit and orbital.

    Answer:

    	Orbits	Orbitals
    1	The orbit is the circula path in which electrons revolves around the nucleus	The orbitals is the particular area in which the electrons are actually present
    2	In orbits electrons show planar motion	In orbitals electrons shows rotational motion
    3	Ori\bits are circular	S orbitals are circular
    4	Orbits are non directional	The orbitals are directional except s orbital

16. iii. What are electrolytes and non-electrolytes?

    Answer:

    A) Electrolytes: Electrolytes are the chemical compounds that can be break down when dissolved in the water & can conduct electricity through their aqueous solution e.g..  Acids, bases & salts.

    B) Non Electrolytes:

    Non electrolytes are the chemical compounds whose aqueous solutions don’t conduct electricity eg. Fats, sugars.

17. iv. Define chemical bond. What is the cause of chemical combination?

    Answer:

    Chemical bonds hold the molecules together & create temporary connections that are essential in our daily life.

    Types of chemical bonds are ionic, covalent, hydrogen bonds & London dispersion forces.

    Cause: The answer to this that atoms are trying to reach the most stable (lowest energy) state that they can. Many atoms become stable when their valence shell is filled with electrons or when they satisfy the octet rule.

    If atom’s doesn’t have this arrangement then they want to achieve by gaining or losing electrons or via sharing electrons through bonds.

18. v. What are the advantages of long form of periodic table?

    Answer:

    i. It gives suitable link between the position of element & its electronic configuration

    ii. On the basis of the atomic number it is easier to remember all the elements

    iii. The element in the same group have similar poperties due t their outer most (Valence shell) configuration.

    iv. It has made the study of the elements systematic and simple.

19. vi. Differentiate between temporary and permanent hardness of water.

    Answer:

    S. No	Temporary Hardness	Permanent Hardness
    1	It is due to the presence of the bicarbonate of calcium & magnesium	It is due to presence of chlorides of sulphates of calcium & magnesium
    2	It can be removed by boiling	It can’t be removed by boiling
    3	Hardness removal is cheaper	Hardness removal is expensive

21. vii. Define the terms Electron, Proton and Neutron.

    Answer:

    Electron : It is the smallest particle present in the orbital of the atoms which revolves around the nucleus. It is negatively charged particle and mass around 9.1 X 10^-31 kg and is discovered by Thomson.

     

    Proton: It is positively charged particle and is present inside the nucleus.It is found in the nucleus with neutrons. In any element No. Of protons & no. Of neutrons are same. Mass of te proton is around 1.67 X 10^-24 Kg and is discovered by Rutherford.

     

    Neutron : It is a neutral particle which is present in the nucleus. It is discovered by Chadwick and mass of neutron is equal to the mass of proton.

22. viii. Explain scale and sludge formation.

    Answer:

     In boilers water evaporates continuously and the concentration of dissolved salts increases progressively. When their concentrations reach saturation point, they are thrown out of water in the form  of precipitates on the inner walls of the boiler. If the precipitation takes place in the form of  losse and simply precipitate it is called “sludge” . On the other hand, if the precipitated matter forms a hard, adhering crust/ coating on the inner walls of the boiler, it is called “scale”.

23. ix. Calculate the percentage composition of various elements in C₂H₂O₄.[Atomic mass of C=12, H=1 and O=16]

    Answer:

          COOH                                                     molecular mass of C₂H₂O₄

           I                                                               =12x2+2x1+16x4

          COOH                                                      =24+2+64

    Oxalic acid                                                   =90g

    % Composition of Carbon (C) = 24/90*100 = 26.66 %

    % Component of Hydrogen (H) = 2/90*100= 2.22 %

    % Composition of Oxygen (O) = 64/90*100 = 71.11 %

24. x. How will you define indicator, titration and end point?

    Answer:

    Indicator: It is the substance which changes the color due to change in pH value. Indicators are weak organic acids & bases with complicated structures.

    Titration: It is a laboratory technique used to measure the unknown concentration (molar) of the solution using a known concentration solution. These of several types like acid base titration, volumetric titrations, Iodometric titrations etc.

    End Point: It is the point at which the end of the reaction is marked by some signal.This signal can be the change of the color of an indicator or change in some electrical property that is measured during the reaction.

26. SECTION-C

    Attempt any three questions.             3x10=30
    Q3. a) Name and explain the quantum numbers.

    Answer:

    Quantum numbers are of four types. These are used to describe the probable location of an electron in an atom.

    1. Principal quantum No. (n) : This quantum number describes the electron shell or energy level of an atom. The value of n ranges from 1 to the shell containing the outermost electron of that atom.

    N = 1, 2, 3, 4,......

    Shell = K, L, M, N, ....

    It describes the size of the orbital & how far the electron extends from the nucleus.

     

    2. Azimuthal or Angular quantum No. (l) :  This quantum no. Divides the shell up into the smaller groups of the sub shells called orbital’s The value of n determine the value of the l.

    l = n – 1

    l = 0, 1, ...n

    So Value of l =

    0	1	2	3	4
    S	P	D	F	g

     

    If n = 1, l = 0, First shell has only one orbital whoch is s

    If n = 2, l = 1, s, p

    If n = 3, l = 2, s, p, d

    If  n= 4, l = 3, s, p, d, f

     

    3. Magnetic Quantum No. (m_l) :It splits the sub shells into specific orbital’s. Thus the orbitals describes how an orbitalis oriented in space relative to other orbital.

    m_l = +l..........0..........-l

    Let for p orbital

     l=1

    m_l = +1,0,-1

    So p has 3 sub shells p_x, p_y, p_z

     

    4. Spin Magnetic Quantum No. (M_s) : This quantum number describes the orientation of electron in the orbital.Each orbital consists the maximum two electrons & one have spin  (M_s) +1/2 and one has -1/2.

27. b) Explain the process of electroplating?

    Answer:

    Electroplating is the process of plating one metal on to another by hydrolysis, most commonly used for decorative purpose to prevent the corrosion of metals. There are also specified types of electroplating like copper plating, Silver plating etc.For example if iron is connected with those metals which are active metals ( Mg or Zn)either directly through a wire. The iron objects act as cathode & protecting metal act as anode. Hence protecting metal loses the electrons and is gradually used up the iron metal is getting protecting from rusting as long as some of active metal is present.

28. Q4. a) Explain molarity, normality and molality

    Answer:

    Molarity: It is defined as the no of moles of the solute dissolved per litre of the solution. It is denoted by M.

    M = No of moles of the solute/ Volume of the solution in litre

    Normality: It is defined no of grams equivalents of the solute dissolved per litre of the solution.. It is denoted by N. N = No of grams equivalent of solute/ Volume of the solution in litre

    Molality: It is defined as the no of the Molar of the solute dissolved in 1000g of the solvent. It is denoted by m. M = No of the moles of the solute/Mass of the solvent in g

29. b) Write a short note on aufbau principle and hund’s rule.

    Answer:

    1. Aufbau Principle: The Aufbau principle says that the arrangement of the electrons in an atom – the electronic configuration is best understood if it is built from the ground up. When we are writing down the electronic configuration of any atom we begin at the lowest energy level and add electrons to higher energy levels.

          

     

    Hund’s principle: It states that the lowest energy electronic configuration, the ground state, in any electron sub shell is the one with the greatest number of the parallel electron spins.

             

                                                                                                                                                                                             

                1                                  2                                  3

    According to Hund’s rule option 2 has greater parallel electronic spin and has lowest energy.

31. Q5. a) Differentiate between alkane and alkyne

    Answer:

    S.No	Alkane	Alkyne
    1	It is the single bond present in the carbon atoms	It is the triple bond present in the carbon atoms
    2	General formula is CnH2n+2	General formula is Cn H2n-2
    3	Carbon is sp3 hybridised	Carbon is sp hybridised

     

32. b) Differentiate between 1s and 2s orbital.

    Answer:

    1s orbital is part of K shell first orbital from the nucleus and have more interaction from the nucleus & have more interaction from the nucleus. 1s is smaller in size as compared to 2s.

    2s orbital is part of L shell and second orbital from nucleus.

33. c) Balance the following equation by hit and trial method 
    NaOH + Cl₂ ---- NaCl +NaClO₃ + H₂O

    Answer:

    6NaOH + 3Cl₂ à 5Nacl + 3H₂O

34. Q6. a) Write the formula of the following compound.

    i)Acetic acid      ii)Acetaldehyde      iii)Acetone      iv)Ethene      v)Ethyne

    Answer:

    S.No	Name	Formula
    1	Acetic Acid	CH3COOH
    2	Acetaldehyde	CH3CHO
    3	Acetone	O          ‖ CH3-C-CH3
    4	Ethene	CH2=CH2
    5	Ethyne	CH=CH

36. b) Differentiate between compound and mixture?

    Answer:

    S. No	Compound	Mixture
    1	Combination of two or more elements	Elements or compounds just mix together to form a mixture and no new compound formed
    2	Composition of new substance is always fixed	Mixture have Variable composition
    3	New substance has total different properties	Shows the properties of constituent particle

37. c) What are the causes of hardness of water?

    Answer:

    Hardness of water is caused by the minerals such as magnesium carbonates & calcium carbonates

38. Q7. a) Define covalent bond. Explain it taking at least 2 examples?

    Answer:

    Covalent Bond: The interatomic linkage that results from the sharing of an electron pair between two atoms. A covalent forms when the bonded atoms have a lower total energy than that of widely separated atoms.

    e.g.

    

    Here carbon atom has 4 valance electrons and make bond with 4 hydrogen atoms to complete its octet

                           

    Here oxygen atom has 6 valance electrons and make bond with 2 hydrogen atoms to complete its octet.

39. b) What is hybridization? What are the main characteristics of hybridization?

    Answer:

    Hybridisation: When the atomic orbital’s are intermixing with each other and making new orbital’s which are of same shape, energy, characteristics which are known as hybridised orbital’s & process is known as hybridisation.                     

     + =

        S                      p                                            sp³

      Atomic Orbitals                     Hybridised Orbitals

    Characteristics

    1. No of the atomic orbital’s take part in the hybridisation is equal to No of the hybridised orbitals.
    2. Hybridised orbital’s make more stable bonds as compared to pure atomic orbitals.
    3. Orbitals belonging to the same atom or ion having similar energies got hybridised.