Other Chemistry · JEE Main previous year questions

Radius of the first excited state of Helium ion is given as : ${\mathrm{a}}_0\to$ radius of first stationary state of hydrogen atom.

1. A.$\mathrm{r}=\frac{{\mathrm{a}}_0}{4}$
2. B.$\mathrm{r}=2{\mathrm{a}}_0$
3. C.$\mathrm{r}=4{\mathrm{a}}_0$
4. D.$\mathrm{r}=\frac{{\mathrm{a}}_0}{2}$

Which of the following statement is not true for radioactive decay?

1. A.Half life is $\ln 2$ times of $\frac{1}{\text{rate constant}}$.
2. B.Decay constant increases with increase in temperature.
3. C.Decay constant does not depend upon temperature.
4. D.Amount of radioactive substance remained after three half lives is $\frac{1}{8}\text{ th}$ of original amount.

Some ${\mathrm{CO}}_2$ gas was kept in a sealed container at a pressure of $1\text{ atm}$ and at $273\text{ K}$ . This entire amount of ${\mathrm{CO}}_2$ gas was later passed through an aqueous solution of $\mathrm{Ca}(\mathrm{OH}{)}_2$. The excess unreacted $\mathrm{Ca}(\mathrm{OH}{)}_2$ was later neutralized with $0.1\text{ M}$ of $40\text{ mL HCl}$ . If the volume of the sealed container of ${\mathrm{CO}}_2$ was $x$, then $x$ is _________ ${\text{cm}}^3$ (nearest integer). [Given : The entire amount of ${\mathrm{CO}}_2(\mathrm{g})$ reacted with exactly half the initial amount of $\mathrm{Ca}(\mathrm{OH}{)}_2$ present in the aqueous solution.]

1. A.Molarity of ${\mathrm{K}}_2\mathrm{C}{\mathrm{r}}_2{\mathrm{O}}_7$ solution is lowered.
2. B.Green colour formation observed on side Y.
3. C.Molarity of $\mathrm{CuS}{\mathrm{O}}_4$ solution is lowered.
4. D.Green colour formation observed on side X.

The ${\mathrm{F}}^{-}$ ions make the enamel on teeth much harder by converting hydroxyapatite (the enamel on the surface of teeth) into much harder fluoroapatite having the formula.

1. A.$[3(\mathrm{C}{\mathrm{a}}_3(\mathrm{P}{\mathrm{O}}_4{)}_2)\cdot \mathrm{Ca}{\mathrm{F}}_2]$
2. B.$[3(\mathrm{C}{\mathrm{a}}_3(\mathrm{P}{\mathrm{O}}_4{)}_2)\cdot \mathrm{Ca}(\mathrm{OH}{)}_2]$
3. C.$[3(\mathrm{C}{\mathrm{a}}_3(\mathrm{P}{\mathrm{O}}_4{)}_3)\cdot \mathrm{Ca}{\mathrm{F}}_2]$
4. D.$[3(\mathrm{C}{\mathrm{a}}_2(\mathrm{P}{\mathrm{O}}_4{)}_2)\cdot \mathrm{Ca}(\mathrm{OH}{)}_2]$

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

1. A.(E) < (D) < (C) < (B) < (A)
2. B.(B) < (D) < (A) < (C) < (E)
3. C.(D) < (E) < (C) < (B) < (A)
4. D.(E) < (D) < (B) < (A) < (C)

The total number of species from the following in which one unpaired electron is present, is ____. ${\mathrm{N}}_2,{\mathrm{O}}_2,{\mathrm{C}}_2^{-},{\mathrm{O}}_2^{-},{\mathrm{O}}_2^{2-},{\mathrm{H}}_2^{+},\mathrm{C}{\mathrm{N}}^{-},\mathrm{H}{\mathrm{e}}_2^{+}$

When equal volume of $1\mathrm{M}\mathrm{HCl}$ and $1\mathrm{M}{\mathrm{H}}_2\mathrm{S}{\mathrm{O}}_4$ are separately neutralised by excess volume of $1\mathrm{M}\mathrm{NaOH}$ solution. $x$ and $y\mathrm{kJ}$ of heat is liberated respectively. The value of $y/x$ is ____.

The heat of solution of anhydrous $\mathrm{CuS}{\mathrm{O}}_4$ and $\mathrm{CuS}{\mathrm{O}}_4\cdot 5{\mathrm{H}}_2\mathrm{O}$ are $-70\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$ and $+12\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$ respectively. The heat of hydration of $\mathrm{CuS}{\mathrm{O}}_4$ to $\mathrm{CuS}{\mathrm{O}}_4\cdot 5{\mathrm{H}}_2\mathrm{O}$ is $-x\mathrm{kJ}$. The value of $x$ is ____. (nearest integer).

The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency '$A$' $\times 10^{12}\mathrm{hertz}$ and that has a radiant intensity in that direction of $\frac{1}{\prime B^{\prime }}$, watt per steradian. '$A$' and '$B$' are respectively

1. A.450 and 683
2. B.540 and $\frac{1}{683}$
3. C.540 and 683
4. D.450 and $\frac{1}{683}$

When $\Delta {\mathrm{H}}_{\mathrm{vap}}=30kJ/mol$ and $\Delta {\mathrm{S}}_{\mathrm{vap}}=75\mathrm{J}\mathrm{mo}{\mathrm{l}}^{-1}{\mathrm{K}}^{-1}$, then the temperature of vapour, at one atmosphere is ____ K.

1. A.Two
2. B.Three
3. C.Four
4. D.One

1. A.can be oxidized to a dicarboxylic acid with $\mathrm{B}{\mathrm{r}}_2$ water
2. B.despite the presence of $-\mathrm{CHO}$ does not give Schiff's test
3. C.will coexist in equilibrium with 2 other cyclic structures
4. D.has 4 asymmetric carbon atoms

Number of molecules from the following which are exceptions to octet rule is ____. $\mathrm{C}{\mathrm{O}}_2,\mathrm{N}{\mathrm{O}}_2,{\mathrm{H}}_2\mathrm{S}{\mathrm{O}}_4,\mathrm{B}{\mathrm{F}}_3,\mathrm{C}{\mathrm{H}}_4,\mathrm{Si}{\mathrm{F}}_4,\mathrm{Cl}{\mathrm{O}}_2,\mathrm{PC}{\mathrm{l}}_5,\mathrm{Be}{\mathrm{F}}_2,{\mathrm{C}}_2{\mathrm{H}}_6,\mathrm{CHC}{\mathrm{l}}_3,\mathrm{CB}{\mathrm{r}}_4$

1. A.(A)-(II), (B)-(IV), (C)-(I), (D)-(III)
2. B.(A)-(I), (B)-(IV), (C)-(II), (D)-(III)
3. C.(A)-(III), (B)-(II), (C)-(I), (D)-(IV)
4. D.(A)-(IV), (B)-(II), (C)-(III), (D)-(I)

Which one of the following compounds will readily react with dilute $\mathrm{NaOH}$ ?

1. A.${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{C}{\mathrm{H}}_2\mathrm{OH}$
2. B.${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}$
3. C.${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{OH}$
4. D.$(\mathrm{C}{\mathrm{H}}_3{)}_3\mathrm{COH}$

The emf of cell $\mathrm{Tl}\left|\underset{(0.001\mathrm{M})}{\mathrm{T}{\mathrm{l}}^{+}}\right|\left|\underset{(0.01\mathrm{M})}{\mathrm{C}{\mathrm{u}}^{2+}}\right|\mathrm{Cu}$ is $0.83\mathrm{V}$ at $298\mathrm{K}$. It could be increased by :

1. A.increasing concentration of $\mathrm{T}{\mathrm{l}}^{+}$ ions
2. B.increasing concentration of $\mathrm{C}{\mathrm{u}}^{2+}$ ions
3. C.increasing concentration of both $\mathrm{T}{\mathrm{l}}^{+}$ and $\mathrm{C}{\mathrm{u}}^{2+}$ ions
4. D.decreasing concentration of both $\mathrm{T}{\mathrm{l}}^{+}$ and $\mathrm{C}{\mathrm{u}}^{2+}$ ions

The correct sequence of acidic strength of the following aliphatic acids in their decreasing order is: $\mathrm{C}{\mathrm{H}}_3\mathrm{C}{\mathrm{H}}_2\mathrm{COOH},\mathrm{C}{\mathrm{H}}_3\mathrm{COOH},\mathrm{C}{\mathrm{H}}_3\mathrm{C}{\mathrm{H}}_2\mathrm{C}{\mathrm{H}}_2\mathrm{COOH},\mathrm{HCOOH}$

1. A.$\mathrm{HCOOH}>\mathrm{C}{\mathrm{H}}_3\mathrm{C}{\mathrm{H}}_2\mathrm{C}{\mathrm{H}}_2\mathrm{COOH}>\mathrm{C}{\mathrm{H}}_3\mathrm{C}{\mathrm{H}}_2\mathrm{COOH}>\mathrm{C}{\mathrm{H}}_3\mathrm{COOH}$
2. B.$\mathrm{HCOOH}>\mathrm{C}{\mathrm{H}}_3\mathrm{COOH}>\mathrm{C}{\mathrm{H}}_3\mathrm{C}{\mathrm{H}}_2\mathrm{COOH}>\mathrm{C}{\mathrm{H}}_3\mathrm{C}{\mathrm{H}}_2\mathrm{C}{\mathrm{H}}_2\mathrm{COOH}$
3. C.$\mathrm{C}{\mathrm{H}}_3\mathrm{C}{\mathrm{H}}_2\mathrm{C}{\mathrm{H}}_2\mathrm{COOH}>\mathrm{C}{\mathrm{H}}_3\mathrm{C}{\mathrm{H}}_2\mathrm{COOH}>\mathrm{C}{\mathrm{H}}_3\mathrm{COOH}>\mathrm{HCOOH}$
4. D.$\mathrm{C}{\mathrm{H}}_3\mathrm{COOH}>\mathrm{C}{\mathrm{H}}_3\mathrm{C}{\mathrm{H}}_2\mathrm{COOH}>\mathrm{C}{\mathrm{H}}_3\mathrm{C}{\mathrm{H}}_2\mathrm{C}{\mathrm{H}}_2\mathrm{COOH}>\mathrm{HCOOH}$

For a reaction $A\stackrel{{\mathrm{K}}_1}{\to }\mathrm{B}\stackrel{{\mathrm{K}}_2}{\to }\mathrm{C}$ If the rate of formation of $\mathrm{B}$ is set to be zero then the concentration of $\mathrm{B}$ is given by :

1. A.$({\mathrm{K}}_1-{\mathrm{K}}_2)[\mathrm{A}]$
2. B.$({\mathrm{K}}_1+{\mathrm{K}}_2)[\mathrm{A}]$
3. C.${\mathrm{K}}_1{\mathrm{K}}_2[\mathrm{A}]$
4. D.$({\mathrm{K}}_1/{\mathrm{K}}_2)[\mathrm{A}]$

Wavenumber for a radiation having $5800\text{ A˚}$ wavelength is $x\times 10{\text{ cm}}^{-1}$. The value of $x$ is ______. (Integer answer)

Arrange the following elements in the increasing order of number of unpaired electrons in it. (A) $\text{Sc}$ (B) $\text{Cr}$ (C) $\text{V}$ (D) $\text{Ti}$ (E) $\text{Mn}$ Choose the correct answer from the options given below :

1. A.(A) < (D) < (C) < (B) < (E)
2. B.(A) < (D) < (C) < (E) < (B)
3. C.(B) < (C) < (D) < (E) < (A)
4. D.(C) < (E) < (B) < (A) < (D)

The ratio $\frac{K_p}{K_c}$ for the reaction : ${\text{CO}}_{(g)}+\frac{1}{2}{\text{O}}_{2(g)}\rightleftharpoons {\text{CO}}_{2(g)}$ is :

1. A.$1$
2. B.$(\text{RT}{)}^{1/2}$
3. C.$\text{RT}$
4. D.$\frac{1}{\sqrt{\text{RT}}}$

For hydrogen atom, energy of an electron in first excited state is $-3.4\text{ eV}$. K.E. of the same electron of hydrogen atom is $x\text{ eV}$. Value of $x$ is ________ $\times 10^{-1}\text{ eV}$. (Nearest integer)