Mole Concept & Stoichiometry · JEE Main previous year questions

A solution of two components containing $n_1$ moles of the $1^{\text{st}}$ component and $n_2$ moles of the $2^{\text{nd}}$ component is prepared. $M_1$ and $M_2$ are the molecular weights of component 1 and 2 respectively. If d is the density of the solution in $\mathrm{g}\mathrm{m}{\mathrm{L}}^{-1}$, $C_2$ is the molarity and $x_2$ is the mole fraction of the $2^{\text{nd}}$ component, then $C_2$ can be expressed as :

1. A.$C_2=\frac{1000x_2}{M_1+x_2(M_2-M_1)}$
2. B.$C_2=\frac{1000d{x}_2}{M_1+x_2(M_2-M_1)}$
3. C.$C_2=\frac{d{x}_2}{M_1+x_2(M_2-M_1)}$
4. D.$C_2=\frac{d{x}_1}{M_1+x_2(M_2-M_1)}$

A solution of phenol in chloroform when treated with aqueous NaOH gives compound P as a major product. The mass percentage of carbon in P is ______. (to the nearest integer) (Atomic mass : C = 12; H = 1; O = 16)

1. A.
2. B.
3. C.
4. D.

The strengths of 5.6 volume hydrogen peroxide (of density 1 g/mL) in terms of mass percentage and molarity (M), respectively, are: (Take molar mass of hydrogen peroxide as 34 g/mol)

1. A.0.85 and 0.5
2. B.0.85 and 0.25
3. C.1.7 and 0.25
4. D.1.7 and 0.5

Complex A has a composition of ${\mathrm{H}}_{12}{\mathrm{O}}_6\mathrm{C}{\mathrm{l}}_3\mathrm{Cr}$. If the complex on treatment with $\text{conc.}{\mathrm{H}}_2\mathrm{S}{\mathrm{O}}_4$ loses $13.5\%$ of its original mass, the correct molecular formula of A is : [Given: atomic mass of $\mathrm{Cr}=52\mathrm{amu}$ and $\mathrm{Cl}=35\mathrm{amu}$]

1. A.$[\mathrm{Cr}({\mathrm{H}}_2\mathrm{O}{)}_5\mathrm{Cl}]\mathrm{C}{\mathrm{l}}_2\cdot {\mathrm{H}}_2\mathrm{O}$
2. B.$[\mathrm{Cr}({\mathrm{H}}_2\mathrm{O}{)}_4\mathrm{C}{\mathrm{l}}_2]\mathrm{Cl}\cdot 2{\mathrm{H}}_2\mathrm{O}$
3. C.$[\mathrm{Cr}({\mathrm{H}}_2\mathrm{O}{)}_3\mathrm{C}{\mathrm{l}}_3]\cdot 3{\mathrm{H}}_2\mathrm{O}$
4. D.$[\mathrm{Cr}({\mathrm{H}}_2\mathrm{O}{)}_6]\mathrm{C}{\mathrm{l}}_3$

A mixture of one mole each of ${\mathrm{H}}_2$ , $\mathrm{He}$ and ${\mathrm{O}}_2$ each are enclosed in a cylinder of volume $V$ at temperature $T$. If the partial pressure of ${\mathrm{H}}_2$ is $2\mathrm{atm}$, the total pressure of the gases in the cylinder is :

1. A.$14\mathrm{atm}$
2. B.$38\mathrm{atm}$
3. C.$6\mathrm{atm}$
4. D.$22\mathrm{atm}$

$6.023\times 10^{22}$ molecules are present in $10\mathrm{g}$ of a substance 'x'. The molarity of a solution containing $5\mathrm{g}$ of substance 'x' in $2\mathrm{L}$ solution is ____ $\times 10^{-3}$

Two compounds A and B with same molecular formula (${\mathrm{C}}_3{\mathrm{H}}_6\mathrm{O}$) undergo Grignard's reaction with methylmagnesium bromide to give products C and D. Products C and D show following chemical tests. | Test | C | D | | :--- | :--- | :--- | | Ceric ammonium nitrate Test | Positive | Positive | | Lucas Test | Turbidity obtained after five minutes | Turbidity obtained immediately | | Iodoform Test | Positive | Negative | C and D respectively are :

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

The ratio of the mass percentages of ‘C & H’ and ‘C & O’ of a saturated acyclic organic compound ‘X’ are 4 : 1 and 3 : 4 respectively. Then, the moles of oxygen gas required for complete combustion of two moles of organic compound ‘X’ is ________.

The hardness of a water sample containing $10^{-3}\text{ M }\mathrm{MgS}{\mathrm{O}}_4$ expressed as $\mathrm{CaC}{\mathrm{O}}_3$ equivalents (in ppm) is _______. (molar mass of $\mathrm{MgS}{\mathrm{O}}_4$ is $120.37\text{ g/mol}$)

The molarity of $\mathrm{HN}{\mathrm{O}}_3$ in a sample which has density 1.4 g/mL and mass percentage of 63% is _______. (Molecular Weight of $\mathrm{HN}{\mathrm{O}}_3=63$)

The first and second ionisation enthalpies of a metal are 496 and $4560{\text{ kJ mol}}^{-1}$, respectively. How many moles of $\mathrm{HCl}$ and ${\mathrm{H}}_2\mathrm{S}{\mathrm{O}}_4$, respectively, will be needed to react completely with 1 mole of the metal hydroxide ?

1. A.1 and 2
2. B.1 and 0.5
3. C.1 and 1
4. D.2 and 0.5

Biochemical Oxygen Demand (BOD) is the amount of oxygen required (in ppm) :

1. A.for sustaining life in a water body.
2. B.by anaerobic bacteria to breakdown inorganic waste present in a water body.
3. C.for the photochemical breakdown of waste present in $1{\text{ m}}^3$ volume of a water body.
4. D.by bacteria to break-down organic waste in a certain volume of a water sample.

10.30 mg of ${\mathrm{O}}_2$ is dissolved into a liter of sea water of density 1.03 g/mL. The concentration of ${\mathrm{O}}_2$ in ppm is_______.

1. A.$\mathrm{XY},2\times 10^{-6}{\mathrm{M}}^3$
2. B.$\mathrm{X}{\mathrm{Y}}_2,1\times 10^{-9}{\mathrm{M}}^3$
3. C.$\mathrm{X}{\mathrm{Y}}_2,4\times 10^{-9}{\mathrm{M}}^3$
4. D.${\mathrm{X}}_2\mathrm{Y},2\times 10^{-9}{\mathrm{M}}^3$

The mole fraction of a solvent in aqueous solution of a solute is 0.8. The molality (in ${\text{mol kg}}^{-1}$) of the aqueous solution is :

1. A.$13.88\times 10^{-1}$
2. B.$13.88\times 10^{-3}$
3. C.$13.88$
4. D.$13.88\times 10^{-2}$

5 moles of ${\text{AB}}_2$ weigh $125\times 10^{-3}\text{ kg}$ and 10 moles of ${\text{A}}_2{\text{B}}_2$ weigh $300\times 10^{-3}\text{ kg}$. The molar mass of A (${\text{M}}_{\text{A}}$) and molar mass of B (${\text{M}}_{\text{B}}$) in ${\text{kg mol}}^{-1}$ are:

1. A.${\text{M}}_{\text{A}}=10\times 10^{-3}$ and ${\text{M}}_{\text{B}}=5\times 10^{-3}$
2. B.${\text{M}}_{\text{A}}=25\times 10^{-3}$ and ${\text{M}}_{\text{B}}=50\times 10^{-3}$
3. C.${\text{M}}_{\text{A}}=5\times 10^{-3}$ and ${\text{M}}_{\text{B}}=10\times 10^{-3}$
4. D.${\text{M}}_{\text{A}}=50\times 10^{-3}$ and ${\text{M}}_{\text{B}}=25\times 10^{-3}$

The difference between $\Delta \mathrm{H}$ and $\Delta \mathrm{U}$ ($\Delta \mathrm{H}-\Delta \mathrm{U}$), when the combustion of one mole of heptane(l) is carried out at a temperature T, is equal to :

1. A.- 4 RT
2. B.3 RT
3. C.- 3 RT
4. D.4 RT

What would be the molality of 20% (mass/ mass) aqueous solution of KI? (molar mass of KI $=166\mathrm{g}\mathrm{mo}{\mathrm{l}}^{-1}$)

1. A.1.51
2. B.1.35
3. C.1.08
4. D.1.48

The percentage composition of carbon by mole in methane is :

1. A.80%
2. B.20%
3. C.75%
4. D.25%

5 moles of an ideal gas at 100 K are allowed to undergo reversible compression till its temperature becomes 200 K. If $C_V=28\mathrm{J}{\mathrm{K}}^{-1}\mathrm{mo}{\mathrm{l}}^{-1}$, calculate $\Delta U$ and $\Delta pV$ for this process. ($R=8.0\mathrm{J}{\mathrm{K}}^{-1}\mathrm{mo}{\mathrm{l}}^{-1}$)

1. A.$\Delta U=14\mathrm{kJ}$; $\Delta (pV)=4\mathrm{kJ}$
2. B.$\Delta U=2.8\mathrm{kJ}$; $\Delta (pV)=0.8\mathrm{kJ}$
3. C.$\Delta U=14\mathrm{kJ}$; $\Delta (pV)=18\mathrm{kJ}$
4. D.$\Delta U=14\mathrm{kJ}$; $\Delta (pV)=0.8\mathrm{kJ}$

Water samples with BOD values of 4 ppm and 18 ppm, respectively are :

1. A.Clean and Highly polluted
2. B.Highly polluted and Clean
3. C.Highly polluted and Highly polluted
4. D.Clean and Clean

The volume of gas A is twice than that of gas B. The compressibility factor of gas A is thrice than that of gas B at same temperature. The pressures of the gases for equal number of moles are -

1. A.$2{\mathrm{P}}_{\mathrm{A}}=3{\mathrm{P}}_{\mathrm{B}}$
2. B.$3{\mathrm{P}}_{\mathrm{A}}=2{\mathrm{P}}_{\mathrm{B}}$
3. C.${\mathrm{P}}_{\mathrm{A}}=3{\mathrm{P}}_{\mathrm{B}}$
4. D.${\mathrm{P}}_{\mathrm{A}}=2{\mathrm{P}}_{\mathrm{B}}$

8 g of NaOH is dissolved in 18g of ${\mathrm{H}}_2\mathrm{O}$. Mole fraction of NaOH in solution and molality (in $\mathrm{mol}\mathrm{k}{\mathrm{g}}^{-1}$) of the solution respectively are -

1. A.0.2, 11.11
2. B.0.167, 22.20
3. C.0.167, 11.11
4. D.0.2, 22.20