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Important formulae from Physical Chemistry for JEE, WBJEE and UPSEE

Feb 16, 2018 16:32 IST
    Physical Chemistry: Important formulae
    Physical Chemistry: Important formulae

    Chemistry is a very important subject for any engineering entrance examination i.e., JEE Main, JEE Advanced, UPSEE, WBJEE, VITEEE, SRMJEEE etc. The number of questions asked from Chemistry subject in JEE Main and JEE Advanced are 30 and 36 (18 in each paper) respectively. While in UPSEE and WBJEE, the number of questions asked is 50 and 40 respectively.

    We can broadly divide the Chemistry into three parts i.e.,

    1. Physical Chemistry

    2. Organic Chemistry

    3. Inorganic Chemistry

    About 35% of the total number of questions asked in any engineering entrance exam is from Physical Chemistry. Therefore, Physical Chemistry is a very important part of Chemistry subject.

    JEE Main 2018: Application Form, Dates, Syllabus, Papers and Mock test

    In this article, we are going to provide you some formulae of Physical Chemistry which are very important from the point of view of the examination.

    1. Basic Concepts of Chemistry:

    Basic concepts of chemistry

    Students can find some questions based on the above formulae given below:

    Question:

    Physical Chemistry Question 1

    Solution:

    Physical Chemistry Solution 1

    Question:

    Physical Chemistry Question 2

    Solution:

    Physical Chemistry Solution 2

    2. States of Matter:

    States of Matter

    Students can find some questions based on the above formulae given below:

    Question:

    At a certain temperature, the value of the slope of the plot of osmotic pressure (∏) against concentration (C in mol L–1) of a certain polymer solution is 291R. The temperature at which osmotic pressure is measured is (R is gas constant)

    (A) 271°C

    (B) 18°C

    (C) 564 K

    (D) 18 K

    Solution:

    We have,

    Physical Chemistry Solution 2

    Question:

    A certain container holds 3.87 g neon at STP. What mass of neon will it hold at 100°C and 10 atm?

    (A) 28.2 g

    (B) 32.4 g

    (C) 24.5 g

    (D) 18.6 g

    Solution:

    Physical Chemistry Solution 2

    3. Structure of Atom:

    Structure of Atom

    Students can find some questions based on the above formulae given below:

    Question:

    The wavelength of second Balmer line in Hydrogen spectrum is 600 nm. The wavelength for its third line in Lyman series is

    (A) 800 nm

    (B) 600 nm

    (C) 400 nm

    (D) 120 nm

    Solution:

    Physical Chemistry Solution 2

    Question:

    Physical Chemistry Question 1

    Solution:

    Physical Chemistry Solution 2

    4. Thermodynamics:

    Thermodynamics Important Formulae

    Students can find some questions based on the above formulae given below:

    Question:

    For the reaction X2Y4(I) → 2 XY2(g) at 300 K the values of ΔU and ΔS are 2 kCal and 20 Cal K1 respectively. The value of ΔG for the reaction is

    (A) – 3400 Cal

    (B) 3400 Cal

    (C) – 2800 Cal

    (D) 2000 Cal

    Solution:

    We have the reaction,

    X2Y4(I) → 2 XY2(g)

    Physical Chemistry Solution 2

    5. Equilibrium:      

    Equilibrium Important Formulae

    Students can find some questions based on the above formulae given below:

    Question:

    Physical Chemistry Solution 2

    Solution:

    Physical Chemistry Solution 2

    Question:

    In which of the following mixed aqueous solutions pH = pKa at equilibrium?

    (1) 100 ml of 0.1M CH3COOH + 100 ml of 0.1M CH3COONa

    (2) 100 ml of 0.1M CH3COOH + 50 ml of 0.1M NaOH

    (3) 100 ml of 0.1M CH3COOH + 100 ml of 0.1M NaOH

    (4) 100 ml of 0.1M CH3COOH + 100 ml of 0.1M NH3

    (A) (1) is correct

    (B) (2) is correct

    (C) (3) is correct

    (D) Both (1) and (2) are correct

    Solution:

    Physical Chemistry Solution 2

    Hence, (1) is correct.

    Physical Chemistry Solution 2

    Hence, (2) is correct.

    6. Solutions:

    Solutions Important Formulae

    Students can find some questions based on the above formulae given below:

    Question:

    Lowering of vapour pressure is highest for

    (a) 0.1 M BaCl2

    (b) 0.1 M glucose

    (c) 0.1 M MgSO4

    (d) urea

    Solution:

    Lowering of vapour pressure is directly proportional to the Van't Hoff factor (i).

    For BaCl2,i = 3 (maximum)

    Thus, BaCl2 has highest value relative lowering of vapour pressure.

    Hence, the correct option is (a).

    Question:

    Physical Chemistry Solution 2

    Solution:

    Physical Chemistry Solution 2

    7. Electrochemistry:

    Electrochemistry Important Formulae

    Students can find some questions based on the above formulae given below:

    Question:

    At temperature of 298 K the emf of the following electrochemical cell

    Ag(s) | Ag+ (0.1 M) | |Zn2+(0.1M) | Zn(s) will be (given Eocell= – 1.562 V)

    (a) – 1.532 V

    (b) – 1.503 V

    (c) 1.532 V

    (d) – 3.06 V

    Solution:

    Physical Chemistry Solution 2

    Question:

    Electrolysis of dilute aqueous NaCl solution was carried out by passing 10 mA current. The time required to liberate 0.01 mole of H2 gas at the cathode is (1 F = 96500 C moP1)

    (a) 9.65 × 104 s

    (b) 19.3 × 104 s

    (c) 28.95 × 104 s

    (d) 38.6 × 104 s

    Solution:

    Physical Chemistry Solution 2

    8. Chemical Kinetics:

    Chemical Kinetics Important Formulae

    Students can find some questions based on the above formulae given below:

    Question:

    The rate of a reaction doubles when its temperature changes from 300 K to 310 K. Activation energy of such a reaction will be (R= 8.314 JK–1 mol–1 and log 2 = 0.301)                             

    (A) 53.6 kJ mol–1                            

    (B) 48.6 kJ mol–1

    (C) 58.5 kJ mol–1                            

    (D) 60.5 kJ mol–1

    Solution:

    Physical Chemistry Solution 2

    Question:

    During nuclear explosion one of the products is 90Sr with half-life of 28.1 yr. If 1 µg of 90Sr was absorbed in the bones of a newly born body instead of calcium, how much of it will remain after 60 yr, if it is not lost metabolically?

    (A) 0.184 µg

    (B) 0.025 µg

    (C) 0.262 µg

    (D) 0.228 µg

    Solution:

    Physical Chemistry Solution 2

    9. Solid State:

    Primitive unit cells and their possible variations as centered unit cells are given below:

    Solid state Important Formulae

    No. of atoms in unit cells in different possible variation are given below:

    Possible Variations

    Number of atoms per unit cell

    Primitive Cubic Unit Cell

    1

    Body- Centred Cubic Unit Cell

    2

    Face- Centred Cubic Unit Cell

    4

    The packaging efficiency of different crystal structure is given below:

    Crystal Structure

    Packaging Efficiency

    HCP and CCP Structures

    74%

    Body- Centered Cubic Structures

    68%

    Simple Cubic Lattice

    52.4%

    Students can find some questions based on the above formulae given below:

    Question:

    Physical Chemistry Solution 2

    Solution:

    Physical Chemistry Solution 2

    Question:

    Physical Chemistry Solution 2

    Solution:

    Physical Chemistry Solution 2

    Most Important Questions for JEE Main & Advanced 2018

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