s Block Elements JEE Main previous year questions with solutions

5 solved JEE Main questions on s Block Elements, free to read — no sign-in needed. The full chapter has 134 questions; sign in to attempt the remaining 129 in the exam simulator.

1. Q1JEE Main 2026 (06 Apr, Shift 1)
   First and second ionization enthalpies of lithium are $520$ kJ mol$^{-1}$ and $7297$ kJ mol$^{-1}$ respectively. Energy required to convert $3.5$ mg lithium (g) into $\text{Li}^{2+}$(g) $[\text{Li(g)} \rightarrow \text{Li}^{2+}\text{(g)}]$ is _______ kJ mol$^{-1}$. (nearest integer) [Molar mass of Li $= 7$ g mol$^{-1}$]
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   Answer: 4

   The total energy required to convert $1$ mole of $\text{Li(g)}$ to $\text{Li}^{2+}\text{(g)}$ is the sum of the first and second ionization enthalpies: $E = IE_1 + IE_2 = 520 + 7297 = 7817 \text{ kJ mol}^{-1}$ Given mass of lithium $= 3.5 \text{ mg} = 3.5 \times 10^{-3} \text{ g}$ Number of moles of lithium $= \dfrac{3.5 \times 10^{-3} \text{ g}}{7 \text{ g mol}^{-1}} = 5 \times 10^{-4} \text{ mol}$ Energy required for $5 \times 10^{-4} \text{ mol}$ of Li is: $\text{Energy} = 5 \times 10^{-4} \text{ mol} \times 7817 \text{ kJ mol}^{-1} = 3.9085 \text{ kJ}$ Rounding to the nearest integer, we get $4$ KJ. Answer: $4$
2. Q2JEE Main 2026 (02 Apr, Shift 2)
   The correct set that contains all kinds (basic, acidic, amphoteric and neutral) of oxides is:
   1. A.$Na_2 O, K_2 O, Al_2 O_3$ and $As_2 O_3$
   2. B.$Al_2 O_3, As_2 O_3, CO$ and $NO$
   3. C.$K_2 O, Cl_2 O_7, As_2 O_3$ and $NO$
   4. D.$Na_2 O, N_2 O, Al_2 O_3$ and $CO$
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   Answer: (C)

   $K_2O$ is a metallic oxide and is basic in nature. $Cl_2O_7$ is a non-metallic oxide with a high oxidation state and is acidic in nature. $As_2O_3$ is a metalloid oxide and is amphoteric in nature. $NO$ is a neutral oxide. Thus, the set $K_2O, Cl_2O_7, As_2O_3$ and $NO$ contains all kinds of oxides. Answer: $K_2 O, Cl_2 O_7, As_2 O_3$ and $NO$
3. Q3JEE Main 2023 (15 Apr, Shift 1)
   Given below are two statements: One is labelled as Assertion $A$ and the other is labelled as Reason $R$: Assertion (A) : ${BeCl}_{2}$ and ${MgCl}_{2}$ produce characteristic flame Reason (R) : The excitation energy is high in ${BeCl}_{2}$ and ${MgCl}_{2}$ In the light of the above statements, choose the correct answer from the options given below:
   1. A.$\left(A\right)$ is true but $\left(R\right)$ is false
   2. B.Both $\left(A\right)$ and $\left(R\right)$ are true but $\left(R\right)$ is NOT the correct explanation of $\left(A\right)$
   3. C.Both ($\left(A\right)$ and $\left(R\right)$ are true and $\left(R\right)$ is the correct explanation of $\left(A\right)$
   4. D.$\left(A\right)$ is false but $\left(R\right)$ is true
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   Answer: (D)

   In $Be\text{and}Mg$, the electrons are strongly bound. The energy required to excite these electrons is very high. Therefore, when the electron reverts back to its original position, the energy released does not fall in the visible region. Hence, no colour in the flame is seen.
4. Q4JEE Main 2023 (13 Apr, Shift 1)
   $Be(OH{)}_{2}$ reacts with $Sr(OH{)}_{2}$ to yield an ionic salt. Choose the incorrect option related to this reaction from the following
   1. A.Both $Sr$ and $Be$ elements are present in the ionic salt
   2. B.$Be$is tetrahedrally coordinated in the ionic salt
   3. C.The element $Be$ is present in the cationic part of the ionic salt
   4. D.The reaction is an example of acid-base neutralization reaction
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   Answer: (C)

   $Be{\left(OH\right)}_{2}$ has amphoteric nature. $Sr{\left(OH\right)}_{2}$ has basic nature. These two compounds undergo acid-base reaction to get salt, $Be{\left(OH\right)}_{2}+Sr{\left(OH\right)}_{2}⟶{Sr}^{+2}{\left[Be(OH{)}_{4}\right]}^{-2}$ As $Be$ is present in anionic part.
5. Q5JEE Main 2023 (12 Apr, Shift 1)
   The density of alkali metals is in the order
   1. A.$K\lt Cs\lt Na\lt Rb$
   2. B.$Na\lt Rb\lt K\lt Cs$
   3. C.$Na\lt K\lt Cs\lt Rb$
   4. D.$K\lt Na\lt Rb\lt Cs$
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   Answer: (D)

   As we down in a group then its size increases and also volume of the atom increases as the number of electrons and protons increases. But the increase in mass is greater than that of increase in volume so the density which is defined as mass per unit volume will increase generally. Density of alkali metals increases down the group except potassium. Therefore, correct order of density of given alkali metals is $K\lt Na\lt Rb\lt Cs$