Hydrogen & s-Block · JEE Main previous year questions

Given below are two statements: Statement I: Sodium dichromate and potassium dichromate are classified as primary standards in titrimetric analysis. Statement II: Phenolphthalein is a weak base, therefore it dissociates in acidic medium. In the light of the above statements, choose the correct answer from the options given below

1. A.Both Statement I and Statement II are ture
2. B.Both Statement I and Statement II are false
3. C.Statement I is true but Statement II is false
4. D.Statement I is false but Statement II is true

Correct statements from the following are A. Potassium dichromate is an oxidising agent and it oxidises $\mathrm{FeS}{\mathrm{O}}_4$ to $\mathrm{F}{\mathrm{e}}_2(\mathrm{S}{\mathrm{O}}_4{)}_3$ in acidic medium. B. Sodium dichromate can be used as primary standard in volumetric estimation. C. $\mathrm{Cr}{\mathrm{O}}_4^{2-}$ and $\mathrm{C}{\mathrm{r}}_2{\mathrm{O}}_7^{2-}$ are interconvertible in aqueous solution by varying the $\mathrm{pH}$ of the solution. D. $\mathrm{Cr}\text{-}\mathrm{O}\text{-}\mathrm{Cr}$ bond angle in $\mathrm{C}{\mathrm{r}}_2{\mathrm{O}}_7^{2-}$ is $126^{\circ }$. Choose the correct answer from the options given below:

1. A.A, B and C Only
2. B.A, C and D Only
3. C.A and C Only
4. D.B and D Only

The surface of sodium metal is irradiated with radiation of wavelength $x\text{ nm}$. The kinetic energy of ejected electrons is $2.8\times 10^{-20}\text{ J}$. The work function of sodium is $2.3\text{ eV}$. The value of $x$ is ________ $\times 10^2\text{ nm}$. (Nearest integer) (Given : $h=6.6\times 10^{-34}\text{ J s}$ ; $1\text{ eV}=1.6\times 10^{-19}\text{ J}$; $c=3.0\times 10^8{\text{ m s}}^{-1}$)

200 cc of $x\times 10^{-3}\text{M}$ potassium dichromate is required to oxidise 750 cc of 0.6 M Mohr's salt solution in acidic medium. Here $x=$ _____.

14.0 g of calcium metal is allowed to react with excess HCl at 1.0 atm pressure and 273 K . Which of the following statements is incorrect? [Given : Molar mass in $\mathrm{g}\mathrm{mo}{\mathrm{l}}^{-1}$ of $\mathrm{Ca}-40,\mathrm{Cl}-35.5,\mathrm{H}-1$ ]

1. A.The limiting reagent is calcium metal.
2. B.33.3 g of $\mathrm{CaC}{\mathrm{l}}_2$ is produced.
3. C.7.84 L of ${\mathrm{H}}_2$ gas is evolved.
4. D.0.35 mol of ${\mathrm{H}}_2$ gas is evolved.

By usual analysis, 1.00 g of compound (X) gave 1.79 g of magnesium pyrophosphate. The percentage of phosphorus in compound (X) is : (nearest integer) (Given, molar mass in g $\mathrm{mo}{\mathrm{l}}^{-1}$: O = 16, Mg = 24, P = 31)

1. A.40
2. B.30
3. C.20
4. D.50

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

Given below are two statements : Statement (I) : Alcohols are formed when alkyl chlorides are treated with aqueous potassium hydroxide by elimination reaction. Statement (II) : In alcoholic potassium hydroxide, alkyl chlorides form alkenes by abstracting the hydrogen from the $\beta$-carbon. In the light of the above statements, choose the most appropriate answer from the options given below :

1. A.Both Statement I and Statement II are incorrect
2. B.Both Statement I and Statement II are correct
3. C.Statement I is incorrect but Statement II is correct
4. D.Statement I is correct but Statement II is incorrect

The amount of calcium oxide produced on heating $150\mathrm{kg}$ limestone ( $75\%$ pure) is $\underline{}\mathrm{kg}$. (Nearest integer) Given: Molar mass (in ${\mathrm{gmol}}^{-1}$) of Ca-40, O-16, C-12

Mass of magnesium required to produce $220\mathrm{mL}$ of hydrogen gas at STP on reaction with excess of dil. $\mathrm{HCl}$ is Given: Molar mass of $\mathrm{Mg}$ is $24{\mathrm{g}\mathrm{mol}}^{-1}$.

1. A.$0.24\mathrm{mg}$
2. B.$235.7\mathrm{g}$
3. C.$2.444\mathrm{g}$
4. D.$236\mathrm{mg}$

Compounds that should not be used as primary standards in titrimetric analysis are : A. ${\mathrm{Na}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$ B. Oxalic acid C. $\mathrm{NaOH}$ D. ${\mathrm{FeSO}}_4\cdot 6{\mathrm{H}}_2\mathrm{O}$ E. Sodium tetraborate Choose the most appropriate answer from the options given below:

1. A.C, D and E Only
2. B.B and D Only
3. C.D and E Only
4. D.A, C and D Only

The nature of oxide $(\mathrm{Te}{\mathrm{O}}_2)$ and hydride $(\mathrm{Te}{\mathrm{H}}_2)$ formed by $\mathrm{Te}$, respectively are :

1. A.Reducing and basic
2. B.Reducing and acidic
3. C.Oxidising and acidic
4. D.Oxidising and basic

Preparation of potassium permanganate from $\mathrm{Mn}{\mathrm{O}}_2$ involves two step process in which the 1st step is a reaction with $\mathrm{KOH}$ and $\mathrm{KN}{\mathrm{O}}_3$ to produce

1. A.${\mathrm{K}}_3\mathrm{Mn}{\mathrm{O}}_4$
2. B.${\mathrm{K}}_4[\mathrm{Mn}(\mathrm{OH}{)}_6]$
3. C.${\mathrm{K}}_2\mathrm{Mn}{\mathrm{O}}_4$
4. D.$\mathrm{KMn}{\mathrm{O}}_4$

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

During the detection of acidic radical present in a salt, a student gets a pale yellow precipitate soluble with difficulty in ${\text{NH}}_4\text{OH}$ solution when sodium carbonate extract was first acidified with dil. ${\text{HNO}}_3$ and then ${\text{AgNO}}_3$ solution was added. This indicates presence of :

1. A.${\text{I}}^{-}$
2. B.${\text{CO}}_3^{2-}$
3. C.${\text{Cl}}^{-}$
4. D.${\text{Br}}^{-}$

Match List I with List II. | LIST I (Alkali Metal) | LIST II (Emission Wavelength in nm) | | :--- | :--- | | A. Li | I. 589.2 | | B. Na | II. 455.5 | | C. Rb | III. 670.8 | | D. Cs | IV. 780.0 | Choose the correct answer from the options given below :

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

Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R: Assertion A: Alcohols react both as nucleophiles and electrophiles. Reason R: Alcohols react with active metals such as sodium, potassium and aluminum to yield corresponding alkoxides and liberate hydrogen. In the light of the above statements, choose the correct answer from the options given below:

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

The mass of sodium acetate ($\mathrm{C}{\mathrm{H}}_3\mathrm{COONa}$) required to prepare $250\text{ mL}$ of $0.35\text{ M}$ aqueous solution is _________ g. (Molar mass of $\mathrm{C}{\mathrm{H}}_3\mathrm{COONa}$ is $82.02{\text{ g mol}}^{-1}$)

Appearance of blood red colour, on treatment of the sodium fusion extract of an organic compound with $\mathrm{FeS}{\mathrm{O}}_4$ in presence of concentrated ${\mathrm{H}}_2\mathrm{S}{\mathrm{O}}_4$ indicates the presence of element/s

1. A.$\mathrm{Br}$
2. B.$\mathrm{S}$
3. C.$\mathrm{N}\mathrm{and}\mathrm{S}$
4. D.$\mathrm{N}$

Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R : Assertion A : Aryl halides cannot be prepared by replacement of hydroxyl group of phenol by halogen atom. Reason R : Phenols react with halogen acids violently. In the light of the above statements, choose the most appropriate from the options given below :

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

Phenol treated with chloroform in presence of sodium hydroxide, which further hydrolyzed in presence of an acid results

1. A.Salicylic acid
2. B.Benzene-1,2-diol
3. C.2-Hydroxybenzaldehyde
4. D.Benzene-1,3-diol

Given below are two statements : Statement I : Permutit process is more efficient compared to the synthetic resin method for the softening of water. Statement II : Synthetic resin method results in the formation of soluble sodium salts. In the light of the above statements, choose the most appropriate answer from the options given below:

1. A.Statement I is correct but Statement II is incorrect
2. B.Both the Statements I and II are correct
3. C.Both the Statements I and II are incorrect
4. D.Statement I is incorrect but Statement II is correct

$20\text{ mL}$ of calcium hydroxide was consumed when it was reacted with $10\text{ mL}$ of unknown solution of ${\mathrm{H}}_2{\mathrm{SO}}_4$. Also $20\text{ mL}$ standard solution of $0.5\text{ M}$ $\mathrm{HCl}$ containing 2 drops of phenolphthalein was titrated with calcium hydroxide, the mixture showed pink colour when burette displayed the value of $35.5\text{ mL}$ whereas the burette showed $25.5\text{ mL}$ initially. The concentration of ${\mathrm{H}}_2{\mathrm{SO}}_4$ is ___________ M. (Nearest integer)

The density of alkali metals is in the order :

1. A.$\mathrm{Na}<\mathrm{K}<\mathrm{Cs}<\mathrm{Rb}$
2. B.$\mathrm{K}<\mathrm{Na}<\mathrm{Rb}<\mathrm{Cs}$
3. C.$\mathrm{K}<\mathrm{Cs}<\mathrm{Na}<\mathrm{Rb}$
4. D.$\mathrm{Na}<\mathrm{Rb}<\mathrm{K}<\mathrm{Cs}$

Match List I with List II | LIST I Type of Hydride | | LIST II Example | | :--- | :--- | :--- | | A. Electron deficient hydride | I. | $\mathrm{Mg}{\mathrm{H}}_2$ | | B. Electron rich hydride | II. | $\mathrm{HF}$ | | C. Electron precise hydride | III. | ${\mathrm{B}}_2{\mathrm{H}}_6$ | | D. Saline hydride | IV. | $\mathrm{C}{\mathrm{H}}_4$ | Choose the correct answer from the options given below:

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