JEE Main Solved Previous Year Papers

The mass of iron converted into $Fe_3O_4$ by the action of 18 g of steam is :

(Given: Molar mass of H, O and Fe are 1, 16 and 56 g mol$^{-1}$ respectively)

Assume iron is present in excess:

What is the energy (in J atom$^{-1}$) required for the following process?

$$Li^{2+}(g) \rightarrow Li^{3+}(g) + e^{-}$$

(Take the ionization energy for the H atom in the ground state as $2.18 \times 10^{-18}\text{ J atom}^{-1}$)

Given below are two statements:

Statement (I): The correct sequence of bond lengths in the following species is :

$$O_2^+ < O_2 < O_2^- < O_2^{2-}$$

Statement (II): The correct sequence of number of unpaired electrons in the following species is:

$$O_2 > O_2^+ > O_2^- > O_2^{2-}$$

In the light of the above statements, choose the correct answer from the options given below:

Consider the following data.

(i) $2Al(s) + 6HCl(aq) \rightarrow Al_2Cl_6(aq) + 3H_2(g) + 1200\text{ kJ/mol}$
(ii) $H_2(g) + Cl_2(g) \rightarrow 2HCl(g) + 164\text{ kJ/mol}$
(iii) $HCl(g) + aq \rightarrow HCl(aq) + 83\text{ kJ/mol}$
(iv) $Al_2Cl_6(s) + aq \rightarrow Al_2Cl_6(aq) + 663\text{ kJ/mol}$

The enthalpy of formation of anhydrous solid $Al_2Cl_6$ is:

19.5 g of fluoro acetic acid (molar mass = 78 g mol$^{-1}$) is dissolved in 500 g of water at 298 K. The depression in the freezing point of water was $1^{\circ}\text{C}$. What is $K_a$ of fluoro acetic acid ?

(For water, $K_f = 1.86\text{ K kg mol}^{-1}$) Assume molarity and molality to have same values.

The solubility product constants of $Ag_2CrO_4$ and $AgBr$ are $32x$ and $4y$ respectively at 298 K. The value of $\left(\frac{\text{molarity of } Ag_2CrO_4}{\text{molarity of } AgBr}\right)$ can be expressed as:

An electrochemical cell is constructed using half cells in the direction of spontaneous change

$$Fe(OH)_2(s) + 2e^- \rightarrow Fe(s) + 2OH^-(aq), \quad E^{\circ} = -0.88\text{ V}$$

and

$$AgBr(s) + e^- \rightarrow Ag(s) + Br^-(aq), \quad E^{\circ} = +0.07\text{ V}$$

Which of the following option is correct ?

$t_{100\%}$ is the time required for the 100% completion of the reaction while $t_{1/2}$ is the time required for 50% of the reaction to be completed. Which of the following option correctly represents the relation between $t_{100\%}$ and $t_{1/2}$ for zero and first order reactions respectively?

Given below are two statements:

Statement (I): The first ionisation enthalpy of the elements Na, Mg, Cl and Ar follows the order

$$Na > Mg > Cl > Ar.$$

Statement (II): Among Ca, Al, Fe and B, the third ionisation enthalpy is very high for Ca.

In the light of the above statements, choose the correct answer from the options given below:

Given below are two statements:

Statement (I): Oxidising power of halogens decreases in the order $F_2 > Cl_2 > Br_2 > I_2$, which is the basis of "Layer test".

Statement (II): "Layer test" to identify $Br_2$ and $I_2$ in aqueous solution involves the oxidation of bromide or iodide into $Br_2$ or $I_2$ respectively with $Cl_2$, which is a type of displacement redox reaction.

In the light of the above statements, choose the correct answer from the options given below:

Which of the following sets includes all the species that will change the orange colour of $K_2Cr_2O_7$ in acidic medium?

Match List - I with List - II.

Choose the correct answer from the options given below :

Given below are two statements:

Statement (I): 1,2,3-Trihydroxypropane can be separated from water by simple distillation.

Statement (II): An azeotropic mixture cannot be separated by fractional distillation.

In the light of the above statements, choose the correct answer from the options given below:

Given below are two statements:

Statement (I): Benzyl chloride reacts faster in $S_N1$ mechanism than ethyl chloride.

Statement (II): Ethyl carbocation intermediate is less stabilized by hyperconjugation than benzyl carbocation by resonance.

In the light of the above statements, choose the correct answer from the options given below:

In IUPAC nomenclature, the correct order of decreasing priority of functional group is:

For the given molecule, "x", the preferred site for the attack of the electrophile is:

Match List - I with List - II.

Choose the correct answer from the options given below:

Consider the three aromatic molecules (P, Q and R) whose structures have been given below:

The correct order regarding the reactivity of these compounds with $Ph-N\equiv N^{(+)}Cl^{(-)}$ under optimum but slightly acidic medium is:

Match List - I with List - II.

Choose the correct answer from the options given below:

A salt with few drops of conc. HCl gives apple green colour in flame test. The group precipitate of the salt is dissolved in acetic acid and treated with $K_2CrO_4$ to give yellow precipitate. When the sodium carbonate extract of the salt solution is heated with conc. $HNO_3$ and ammonium molybdate, it resulted a canary yellow precipitate. The cation and anion present in the salt are respectively,