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Day 21: JEE Mains Chemistry

5 questions. Try each one first, then open its answer.

  1. Question 1

    Chemical Kinetics. This type asked 5 times: 28 Jun 2022, 29 Jul 2022, 29 Jan 2024, 1 Feb 2024, 24 Jan 2026 S2. This one: 24 Jan 2026 S2 See all 5 of this type

    47
    The half-life of  65Zn\ ^{65}Zn is 245 days. After x days, 75%75\% of original activity remained. The value of x in days is ____\_\_\_\_ . (Nearest integer) (Given : log⁡3=0.4771\log3 = 0.4771 and log⁡2=0.3010\log2 = 0.3010 )

  2. Question 2

    Chemical Kinetics. This type asked 5 times: 2021 Paper 20, 25 Jun 2022, 11 Apr 2023, 30 Jan 2024, 23 Jan 2026 S2. This one: 23 Jan 2026 S2 See all 5 of this type

    36
    Observe the following reactions at T(K)T(K) (I) A → products. (II) 5Br−(aq)+BrO3−(aq)+6H+(aq)→3Br2(aq)+3H2O(l)5{Br}^{-}(aq) + {BrO}_{3}^{-}(aq) + 6H^{+}(aq) \rightarrow 3{Br}_{2}(aq) + 3H_{2}O(l) Both the reactions are started at 10.00 am . The rates of these reactions at 10.10 am are same. The value of −Δ[Br−]Δt-\frac{\Delta\left\lbrack Br^{-} \right\rbrack}{\Delta t} at 10.10 am is 2×10−4 mol L−1Min−12 \times10^{- 4}\text{ }mol{\text{ }L}^{- 1}Min^{- 1}. The concentration of A at 10.10 am is 10−2 mol L−110^{- 2}\text{ }mol{\text{ }L}^{- 1}. What is the first order rate constant (in min⁡−1\min^{- 1} ) of reaction I?

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  3. Question 3

    Equilibrium. This type asked 5 times: 2021 Paper 13, 31 Jan 2023, 29 Jan 2024, 6 Apr 2024, 23 Jan 2026 S1. This one: 23 Jan 2026 S1 See all 5 of this type

    45
    Consider the general reaction given below at 400 K
    xA(g)⇌yB(g)xA(g) \rightleftharpoons yB(g)
    The values of KpK_{p} and KcK_{c} are studied under the same condition of temperature but variation in x and y . (I) Kp=85.87K_{p}= 85.87 and Kc=2.586K_{c}= 2.586 appropriate units (II) Kp=0.862K_{p}= 0.862 and Kc=28.62K_{c}= 28.62 appropriate units The value of xx and yy in (I) and (II) respectively are:

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  4. Question 4

    Structure of Atom. This type asked 5 times: 30 Jan 2023, 27 Jan 2024, 4 Apr 2024, 5 Apr 2024, 23 Jan 2026 S1. This one: 23 Jan 2026 S1 See all 5 of this type

    36
    Given, (A) n=5,ml=−1n = 5,m_{l}= - 1 (B) n=3,l=2,ml=−1,ms=+12n = 3,l = 2,m_{l}= - 1,m_{s}= +\frac{1}{2} The maximum number of electron(s) in an atom that can have the quantum numbers as given in (A) and (B) respectively are :

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  5. Question 5

    Chemical Bonding and Molecular Structure. This type asked 5 times: 10 Apr 2023, 13 Apr 2023, 4 Apr 2024, 22 Jan 2025, 22 Jan 2026 S2. This one: 22 Jan 2026 S2 See all 5 of this type

    36
    Among H2 S,H2O,NF3,NH3H_{2}\text{ }S,H_{2}O,NF_{3},NH_{3} and CHCl3CHCl_{3}, identify the molecule (X)(X) with lowest dipole moment value. The number of lone pairs of electrons present on the central atom of the molecule (X)(X) is :

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