Mole Concept & Stoichiometry · JEE Main previous year questions

A solution of sodium sulphate contains $92\text{ g}$ of $\mathrm{N}{\mathrm{a}}^{+}$ ions per kilogram of water. The molality of $\mathrm{N}{\mathrm{a}}^{+}$ ions in that solution in ${\mathrm{mol}\mathrm{kg}}^{-1}$ is :

1. A.12
2. B.4
3. C.8
4. D.16

A water sample has ppm level concentration of the following metals : Fe = 0.2; Mn = 5.0; Cu = 3.0; Zn = 5.0. The metal that makes the water sample unsuitable for drinking is :

1. A.Cu
2. B.Mn
3. C.Fe
4. D.Zn

$0.5\text{ moles}$ of gas A and x moles of gas B exert a pressure of $200\text{ Pa}$ in a container of volume $10{\text{ m}}^3$ at $1000\text{ K}$. Given R is the gas constant in ${\mathrm{JK}}^{-1}{\mathrm{mol}}^{-1}$, x is :

1. A.$\frac{2R}{4+R}$
2. B.$\frac{2R}{4-R}$
3. C.$\frac{4+R}{2R}$
4. D.$\frac{4-R}{2R}$

An unknown chlorohydrocarbon has 3.55% of chlorine. If each molecule of the hydrocarbon has one chlorine atom only; chlorine atoms present in $1\mathrm{g}$ of chlorohydrocarbon are : (Atomic wt. of $\mathrm{Cl}=35.5\mathrm{u}$; Avogadro constant $=6.023\times 10^{23}\mathrm{mo}{\mathrm{l}}^{-1}$)

1. A.$6.023\times 10^{20}$
2. B.$6.023\times 10^9$
3. C.$6.023\times 10^{21}$
4. D.$6.023\times 10^{23}$

The ratio of mass percent of C and H of an organic compound $({\text{C}}_{\text{X}}{\text{H}}_{\text{Y}}{\text{O}}_{\text{Z}})$ is $6:1$. If one molecule of the above compound $({\text{C}}_{\text{X}}{\text{H}}_{\text{Y}}{\text{O}}_{\text{Z}})$ contains half as much oxygen as required to burn one molecule of compound ${\text{C}}_{\text{X}}{\text{H}}_{\text{Y}}$ completely to ${\text{CO}}_2$ and ${\text{H}}_2\text{O}$. The empirical formula of compound ${\text{C}}_{\text{X}}{\text{H}}_{\text{Y}}{\text{O}}_{\text{Z}}$ is

1. A.${\text{C}}_2{\text{H}}_4{\text{O}}_3$
2. B.${\text{C}}_3{\text{H}}_6{\text{O}}_3$
3. C.${\text{C}}_2{\text{H}}_4\text{O}$
4. D.${\text{C}}_3{\text{H}}_4{\text{O}}_2$

A solution is prepared by mixing 8.5 g of $\mathrm{C}{\mathrm{H}}_2\mathrm{C}{\mathrm{l}}_2$ and 11.95 g of $\mathrm{CHC}{\mathrm{l}}_3$ . If vapour pressure of $\mathrm{C}{\mathrm{H}}_2\mathrm{C}{\mathrm{l}}_2$ and $\mathrm{CHC}{\mathrm{l}}_3$ at 298 K are 415 and 200 mmHg respectively, the mole fraction of $\mathrm{CHC}{\mathrm{l}}_3$ in vapour form is : (Molar mass of $\mathrm{Cl}=35.5\mathrm{g}\mathrm{mo}{\mathrm{l}}^{-1}$)

1. A.$0.162$
2. B.$0.675$
3. C.$0.325$
4. D.$0.486$

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

Excess of $\mathrm{NaOH}$ (aq) was added to 100 mL of $\mathrm{FeC}{\mathrm{l}}_3$ (aq) resulting into 2.14 g of $\mathrm{Fe}(\mathrm{OH}{)}_3$ . The molarity of $\mathrm{FeC}{\mathrm{l}}_3$ (aq) is : (Given molar mass of $\mathrm{Fe}=56\mathrm{g}\mathrm{mo}{\mathrm{l}}^{-1}$ and molar mass of $\mathrm{Cl}=35.5\mathrm{g}\mathrm{mo}{\mathrm{l}}^{-1}$)

1. A.$0.2\mathrm{M}$
2. B.$0.3\mathrm{M}$
3. C.$0.6\mathrm{M}$
4. D.$1.8\mathrm{M}$

The heats of combustion of carbon and carbon monoxide are $-393.5$ and $-283.5\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$, respectively. The heat of formation (in $\mathrm{kJ}$) of carbon monoxide per mole is :

1. A.$676.5$
2. B.$-676.5$
3. C.$-110$
4. D.$110.5$

The molecular formula of a commercial resin used for exchanging ions in water softening is ${\mathrm{C}}_8{\mathrm{H}}_7\mathrm{S}{\mathrm{O}}_3\mathrm{Na}$ (Mol. Wt. 206). What would be the maximum uptake of $\mathrm{C}{\mathrm{a}}^{2+}$ ions by the resin when expressed in mole per gram resin?

1. A.2/309
2. B.1/412
3. C.1/103
4. D.1/206

For the non – stoichiometre reaction $2\mathrm{A}+\mathrm{B}\to \mathrm{C}+\mathrm{D}$, the following kinetic data were obtained in three separate experiments, all at $298\mathrm{K}$. | Initial Concentration (A) | Initial Concentration (B) | Initial rate of formation of C ($\mathrm{mol}{\mathrm{L}}^{-1}{\mathrm{s}}^{-1}$) | | :--- | :--- | :--- | | $0.1\mathrm{M}$ | $0.1\mathrm{M}$ | $1.2\times 10^{-3}$ | | $0.1\mathrm{M}$ | $0.2\mathrm{M}$ | $1.2\times 10^{-3}$ | | $0.2\mathrm{M}$ | $0.1\mathrm{M}$ | $2.4\times 10^{-3}$ | The rate law for the formation of C is:

1. A.$\frac{dc}{dt}=k[A][B{]}^2$
2. B.$\frac{dc}{dt}=k[A]$
3. C.$\frac{dc}{dt}=k[A][B]$
4. D.$\frac{dc}{dt}=k[A{]}^2[B]$

One mole of an ideal gas is expanded isothermally and reversibly to half of its initial pressure. $\Delta S$ for the process in $\mathrm{J}{\mathrm{K}}^{-1}\mathrm{mo}{\mathrm{l}}^{-1}$ is $[\ln 2=0.693\text{ and }R=8.314J/(\mathrm{mol}\mathrm{K})]$

1. A.6.76
2. B.5.76
3. C.10.76
4. D.8.03

One mole of ${\mathrm{O}}_{2(\mathrm{g})}$ and two moles of $\mathrm{S}{\mathrm{O}}_{2(\mathrm{g})}$ were heated in a closed vessel of one-litre capacity at 1098 K. At equilibrium 1.6 moles of $\mathrm{S}{\mathrm{O}}_{3(\mathrm{g})}$ were found. The equilibrium constant $K_c$ of the reaction would be

1. A.30
2. B.40
3. C.80
4. D.60

The ppm level of ${\mathrm{F}}^{-}$ in a $500\mathrm{g}$ sample of a tooth paste containing $0.2\mathrm{g}{\mathrm{F}}^{-}$ is

1. A.400
2. B.1000
3. C.250
4. D.200

The concentrated sulphuric acid that is peddled commercially is 95% ${\mathrm{H}}_2\mathrm{S}{\mathrm{O}}_4$ by weight. If the density of this commercial acid is $1.834\mathrm{g}\mathrm{c}{\mathrm{m}}^{-3}$, the molarity of this solution is

1. A.17.8 M
2. B.12.0 M
3. C.10.5 M
4. D.15.7 M

The energy required to break one mole of $\mathrm{Cl}-\mathrm{Cl}$ bonds in $\mathrm{C}{\mathrm{l}}_2$ is $242\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$. The longest wavelength of light capable of breaking a single $\mathrm{Cl}-\mathrm{Cl}$ bond is ($\mathrm{c}=3\times 10^8\mathrm{m}{\mathrm{s}}^{-1}$ and ${\mathrm{N}}_{\mathrm{A}}=6.02\times 10^{23}\mathrm{mo}{\mathrm{l}}^{-1}$)

1. A.$594\mathrm{nm}$
2. B.$640\mathrm{nm}$
3. C.$700\mathrm{nm}$
4. D.$494\mathrm{nm}$

One mole of a symmetrical alkene on ozonolysis gives two moles of an aldehyde having a molecular mass of 44 u. The alkene is

1. A.propene
2. B.1–butene
3. C.2–butene
4. D.ethene

If $10^{-4}\mathrm{d}{\mathrm{m}}^3$ of water is introduced into a $1.0\mathrm{d}{\mathrm{m}}^3$ flask at 300 K, how many moles of water are in the vapour phase when equilibrium is established ? (Given : Vapour pressure of ${\mathrm{H}}_2\mathrm{O}$ at 300 K is 3170 Pa ; $\mathrm{R}=8.314\mathrm{J}{\mathrm{K}}^{-1}\mathrm{mo}{\mathrm{l}}^{-1}$)

1. A.$5.56\times 10^{-3}\mathrm{mol}$
2. B.$1.53\times 10^{-2}\mathrm{mol}$
3. C.$4.46\times 10^{-2}\mathrm{mol}$
4. D.$1.27\times 10^{-3}\mathrm{mol}$

The number of stereoisomers possible for a compound of the molecular formula $\mathrm{C}{\mathrm{H}}_3-\mathrm{CH}=\mathrm{CH}-\mathrm{CH}(\mathrm{OH})-\mathrm{Me}$ is :

1. A.2
2. B.4
3. C.6
4. D.3

How many moles of magnesium phosphate $\mathrm{M}{\mathrm{g}}_3(\mathrm{P}{\mathrm{O}}_4{)}_2$ will contain $0.25\mathrm{mole}$ of oxygen atoms?

1. A.$1.25\times 10^{-2}$
2. B.$2.5\times 10^{-2}$
3. C.$0.02$
4. D.$3.125\times 10^{-2}$

Density of a $2.05\mathrm{M}$ solution of acetic acid in water is $1.02g/mL$. The molality of the solution is

1. A.$2.28\mathrm{mol}\mathrm{k}{\mathrm{g}}^{-1}$
2. B.$0.44\mathrm{mol}\mathrm{k}{\mathrm{g}}^{-1}$
3. C.$1.14\mathrm{mol}\mathrm{k}{\mathrm{g}}^{-1}$
4. D.$3.28\mathrm{mol}\mathrm{k}{\mathrm{g}}^{-1}$

Two solutions of a substance (non electrolyte) are mixed in the following manner. 480 ml of 1.5 M first solution + 520 ml of 1.2 M second solution. What is the molarity of the final mixture?

1. A.2.70 M
2. B.1.344 M
3. C.1.50 M
4. D.1.20 M

If we consider that 1/6, in place of 1/12, mass of carbon atom is taken to be the relative atomic mass unit, the mass of one mole of the substance will

1. A.be a function of the molecular mass of the substance
2. B.remain unchanged
3. C.increase two fold
4. D.decrease twice

If the bond dissociation energies of $\mathrm{XY}$, ${\mathrm{X}}_2$ and ${\mathrm{Y}}_2$ (all diatomic molecules) are in the ratio of $1:1:0.5$ and $\Delta H_f$ for the formation of $\mathrm{XY}$ is $-200\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$. The bond dissociation energy of ${\mathrm{X}}_2$ will be :

1. A.$100\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$
2. B.$200\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$
3. C.$300\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$
4. D.$800\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$

An ionic compound has a unit cell consisting of A ions at the corners of a cube and B ions on the centres of the faces of the cube. The empirical formula for this compound would be :

1. A.$\mathrm{AB}$
2. B.${\mathrm{A}}_2\mathrm{B}$
3. C.$\mathrm{A}{\mathrm{B}}_3$
4. D.${\mathrm{A}}_3\mathrm{B}$