Mole Concept & Stoichiometry · JEE Main previous year questions

When a certain amount of solid A is dissolved in $100\mathrm{g}$ of water at $25^{\circ }\mathrm{C}$ to make a dilute solution, the vapour pressure of the solution is reduced to one-half of that of pure water. The vapour pressure of pure water is $23.76\mathrm{mmHg}$. The number of moles of solute A added is ____. (Nearest Integer)

When $800\mathrm{mL}$ of $0.5\mathrm{M}$ nitric acid is heated in a beaker, its volume is reduced to half and $11.5\mathrm{g}$ of nitric acid is evaporated. The molarity of the remaining nitric acid solution is $x\times 10^{-2}\mathrm{M}$. (Nearest integer) (Molar mass of nitric acid is $63\mathrm{g}\mathrm{mo}{\mathrm{l}}^{-1}$)

The amount of charge in $\mathrm{F}$ (Faraday) required to obtain one mole of iron from $\mathrm{F}{\mathrm{e}}_3{\mathrm{O}}_4$ is ____. (Nearest Integer)

The total number of monobromo derivatives formed by the alkanes with molecular formula ${\mathrm{C}}_5{\mathrm{H}}_{12}$ is (excluding stereo isomers) ____ .

An element X has a body centred cubic (bcc) structure with a cell edge of $200\text{ pm}$. The density of the element is $5{\text{ g cm}}^{-3}$. The number of atoms present in $300\text{ g}$ of the element X is ____________. Given : Avogadro constant, $N_A=6.0\times 10^{23}{\text{ mol}}^{-1}$.

1. A.$5{\mathrm{N}}_A$
2. B.$6{\mathrm{N}}_A$
3. C.$15{\mathrm{N}}_A$
4. D.$25{\mathrm{N}}_A$

Compound A contains 8.7% Hydrogen, 74% Carbon and 17.3% Nitrogen. The molecular formula of the compound is, Given : Atomic masses of C, H and N are 12, 1 and 14 amu respectively. The molar mass of the compound A is $162\mathrm{g}\mathrm{mo}{\mathrm{l}}^{-1}$.

1. A.${\mathrm{C}}_4{\mathrm{H}}_6{\mathrm{N}}_2$
2. B.${\mathrm{C}}_2{\mathrm{H}}_3\mathrm{N}$
3. C.${\mathrm{C}}_5{\mathrm{H}}_7\mathrm{N}$
4. D.${\mathrm{C}}_{10}{\mathrm{H}}_{14}{\mathrm{N}}_2$

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A) : At $10^{\circ }\mathrm{C}$, the density of a $5\mathrm{M}$ solution of $\mathrm{KCl}$ [atomic masses of $\mathrm{K}$ & $\mathrm{Cl}$ are 39 & $35.5\mathrm{g}\mathrm{mo}{\mathrm{l}}^{-1}$ respectively], is '$x$' $\mathrm{g}\mathrm{m}{\mathrm{l}}^{-1}$. The solution is cooled to $-21^{\circ }\mathrm{C}$. The molality of the solution will remain unchanged. Reason (R) : The molality of a solution does not change with temperature as mass remains unaffected with temperature. In the light of the above statements, choose the correct answer from the options given below :

1. A.Both (A) and (R) are true and (R) is the correct explanation of (A).
2. B.Both (A) and (R) are true but (R) is not the correct explanation of (A).
3. C.(A) is true but (R) is false.
4. D.(A) is false but (R) is true.

$2\mathrm{NOCl}(\mathrm{g})\rightleftharpoons 2\mathrm{NO}(\mathrm{g})+\mathrm{C}{\mathrm{l}}_2(\mathrm{g})$ In an experiment, $2.0\text{moles}$ of $\mathrm{NOCl}$ was placed in a one-litre flask and the concentration of $\mathrm{NO}$ after equilibrium established, was found to be $0.4mol/L$. The equilibrium constant at $30^{\circ }\mathrm{C}$ is ____ $\times 10^{-4}$.

Two elements A and B which form $0.15\text{moles}$ of ${\mathrm{A}}_2\mathrm{B}$ and $\mathrm{A}{\mathrm{B}}_3$ type compounds. If both ${\mathrm{A}}_2\mathrm{B}$ and $\mathrm{A}{\mathrm{B}}_3$ weigh equally, then the atomic weight of A is ____ times of atomic weight of B.

When $5\text{ moles}$ of He gas expand isothermally and reversibly at $300\text{ K}$ from $10\text{ litre}$ to $20\text{ litre}$, the magnitude of the maximum work obtained is ________ J. [nearest integer] (Given : $\text{R}=8.3{\text{ J K}}^{-1}{\text{ mol}}^{-1}$ and $\log 2=0.3010$)

A commercially sold conc. HCl is 35% HCl by mass. If the density of this commercial acid is 1.46 g/mL, the molarity of this solution is: (Atomic mass : Cl = 35.5 amu, H = 1 amu)

1. A.10.2 M
2. B.12.5 M
3. C.14.0 M
4. D.18.2 M

A flask is filled with equal moles of A and B. The half lives of A and B are 100 s and 50 s respectively and are independent of the initial concentration. The time required for the concentration of A to be four times that of B is ___________ s. (Given : ln 2 = 0.693)

The moles of methane required to produce $81\mathrm{g}$ of water after complete combustion is ____ $\times 10^{-2}\mathrm{mol}$. [nearest integer]

In a solid $\mathrm{AB}$, $\mathrm{A}$ atoms are in ccp arrangement and $\mathrm{B}$ atoms occupy all the octahedral sites. If two atoms from the opposite faces are removed, then the resultant stoichiometry of the compound is ${\mathrm{A}}_{\mathrm{x}}{\mathrm{B}}_{\mathrm{y}}$. The value of $x$ is ____. [nearest integer]

The energy of one mole of photons of radiation of wavelength $300\text{ nm}$ is (Given : $h=6.63\times 10^{-34}\text{ J s}$, $N_{\mathrm{A}}=6.02\times 10^{23}{\text{ mol}}^{-1}$, $c=3\times 10^8{\text{ m s}}^{-1}$)

1. A.$235{\text{ kJ mol}}^{-1}$
2. B.$325{\text{ kJ mol}}^{-1}$
3. C.$399{\text{ kJ mol}}^{-1}$
4. D.$435{\text{ kJ mol}}^{-1}$

In the following sequence of reactions a compound A, (molecular formula ${\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_2$) with a straight chain structure gives a ${\mathrm{C}}_4$ carboxylic acid. A is : $$\mathrm{A}\underset{{\mathrm{H}}_3{\mathrm{O}}^{+}}{\overset{\mathrm{LiAl}{\mathrm{H}}_4}{\to }}\mathrm{B}\stackrel{\mathrm{Oxidation}}{\to }{\mathrm{C}}_4\text{ - carboxylic acid}$$

1. A.$\mathrm{C}{\mathrm{H}}_3-\mathrm{C}{\mathrm{H}}_2-\mathrm{COO}-\mathrm{C}{\mathrm{H}}_2-\mathrm{C}{\mathrm{H}}_2-\mathrm{C}{\mathrm{H}}_3$
2. B.$\mathrm{C}{\mathrm{H}}_3-\mathrm{C}{\mathrm{H}}_2-\mathrm{CH}(\mathrm{OH})-\mathrm{C}{\mathrm{H}}_2-\mathrm{O}-\mathrm{CH}=\mathrm{C}{\mathrm{H}}_2$
3. C.$\mathrm{C}{\mathrm{H}}_3-\mathrm{C}{\mathrm{H}}_2-\mathrm{C}{\mathrm{H}}_2-\mathrm{COO}-\mathrm{C}{\mathrm{H}}_2-\mathrm{C}{\mathrm{H}}_3$
4. D.$\mathrm{C}{\mathrm{H}}_3-\mathrm{C}{\mathrm{H}}_2-\mathrm{C}{\mathrm{H}}_2-\mathrm{O}-\mathrm{CH}=\mathrm{CH}-\mathrm{C}{\mathrm{H}}_2-\mathrm{OH}$

100 mL of $\mathrm{N}{\mathrm{a}}_3\mathrm{P}{\mathrm{O}}_4$ solution contains 3.45 g of sodium. The molarity of the solution is ___________ $\times 10^{-2}{\text{ mol L}}^{-1}$. (Nearest integer) [$\text{Atomic Masses - Na : }23.0\text{ u}$, $\mathrm{O}:16.0\text{ u}$, $\mathrm{P}:31.0\text{ u}$]

3 moles of metal complex with formula $\mathrm{Co}(\mathrm{en}{)}_2\mathrm{C}{\mathrm{l}}_3$ gives 3 moles of silver chloride on treatment with excess of silver nitrate. The secondary valency of Co in the complex is __________. (Round off to the nearest integer)

Three moles of AgCl get precipitated when one mole of an octahedral co-ordination compound with empirical formula $\mathrm{CrC}{\mathrm{l}}_3.3N{\mathrm{H}}_3.3{\mathrm{H}}_2\mathrm{O}$ reacts with excess of silver nitrate. The number of chloride ions satisfying the secondary valency of the metal ion is ____.

To synthesize $1.0\text{ mole}$ of 2-methylpropan-2-ol from Ethylethanoate ________ equivalents of ${\text{CH}}_3\text{MgBr}$ Reagent will be required. (Integer value)

At $20^{\circ }\text{ C}$, the vapour pressure of benzene is $70\text{ torr}$ and that of methyl benzene is $20\text{ torr}$. The mole fraction of benzene in the vapour phase at $20^{\circ }\text{ C}$ above an equimolar mixture of benzene and methyl benzene is ________ $\times 10^{-2}$. (Nearest integer)

Compound with molecular formula ${\mathrm{C}}_3{\mathrm{H}}_6\mathrm{O}$ can show :

1. A.Positional isomerism
2. B.Both positional isomerism and metamerism
3. C.Metamerism
4. D.Functional group isomerism

Complete combustion of 750 g of an organic compound provides 420 g of $\mathrm{C}{\mathrm{O}}_2$ and 210 g of ${\mathrm{H}}_2\mathrm{O}$. The percentage composition of carbon and hydrogen in organic compound is 15.3 and _______ respectively. (Round off to the Nearest Integer).

A 6.50 molal solution of $\mathrm{KOH}$ (aq.) has a density of $1.89{\text{ g cm}}^{-3}$. The molarity of the solution is _______ ${\text{mol dm}}^{-3}$. (Round off to the Nearest Integer). [Atomic masses : $\mathrm{K}:39.0\text{ u}$; $\mathrm{O}:16.0\text{ u}$; $\mathrm{H}:1.0\text{ u}$]

Consider titration of NaOH solution versus 1.25 M oxalic acid solution. At the end point following burette readings were obtained. (i) 4.5 mL (ii) 4.5 mL (iii) 4.4 mL (iv) 4.4 mL (v) 4.4 mL If the volume of oxalic acid taken was 10.0 mL then the molarity of the NaOH solution is ________ M. (Rounded off to the nearest integer)