#
Multiple Choice Questions
One and More than One Correct
1. A solution when diluted with $\text{H}_2\text{O}$ and boiled, it gives a white precipitate. On addition of excess $\text{NH}_4\text{Cl} / \text{NH}_4\text{OH}$, the volume of precipitate decreases leaving behind a white gelatinous precipitate. Identify the precipitate which dissolves in $\text{NH}_4\text{OH} / \text{NH}_4\text{Cl}$. [JEE 2006]
a. $\text{Zn(OH)}_2$
b. $\text{Al(OH)}_3$
c. $\text{Mg(OH)}_2$
d. $\text{Ca(OH)}_2$
Answer: (a)
Solution:
Due to formation of tetraammine zinc (II) complex
$$\text{Zn}^{2+} + 2\text{NH}_4\text{OH} \longrightarrow \text{Zn(OH)}_2 \xrightarrow{\text{NH}_4\text{OH}} [\text{Zn(NH}_3)_4]^{2+}$$2. Extraction of zinc from zinc blende is achieved by [JEE 2007 P-I]
a. electrolytic reduction
b. roasting followed by reduction with carbon
c. roasting followed by reduction with another metal
d. roasting followed by self-reduction
Answer: (b)
Solution:
Option (B) is correct.
3. Native silver metal forms a water soluble complex with a dilute aqueous solution of NaCN in the presence of [JEE 2008 P-I]
a. nitrogen
b. oxygen
c. carbon dioxide
d. argon
Answer: (b)
Solution:
Ag dissociates in a solution of NaCN in the presence of air, forms sodium argentocyanide.
$$4\text{Ag} + 8\text{NaCN} + 2\text{H}_2\text{O} + \text{O}_2 \longrightarrow 4\text{Na}[\text{Ag(CN)}_2] + 4\text{NaOH}$$4. Among the following the coloured compound is [JEE 2008 P-II]
a. $\text{CuCl}$
b. $\text{K}_3[\text{Cu(CN)}_4]$
c. $\text{CuF}_2$
d. $[\text{Cu(CH}_3\text{CN})_4]\text{BF}_4$
Answer: (c)
Solution:
In the crystalline form $\text{CuF}_2$ is blue colored.
5. Oxidation states of the metal in the minerals haematite and magnetite, respectively, are [JEE 2011 P-II]
a. II, III in haematite and III in magnetite
b. II, III in haematite and II in magnetite
c. II in haematite and II, III in magnetite
d. III in haematite and II, III in magnetite
Answer: (d)
Solution:
Haematite: $\text{Fe}_2\text{O}_3 : 2x + 3(-2) = 0 \implies x = 3$
Magnetite: $\text{Fe}_3\text{O}_4$ [an equimolar mixture of $\text{FeO}$ and $\text{Fe}_2\text{O}_3$]
$\text{FeO} : x - 2 = 0 \implies x = 2$
$\text{Fe}_2\text{O}_3 : x = 3$
6. The colour of light absorbed by an aqueous solution of $\text{CuSO}_4$ is [JEE 2012 P-I]
a. orange –red
b. blue –green
c. yellow
d. violet
Answer: (a)
Solution:
The solution is blue. The colour that is absorbed complementary to the colour that is observed.
7. Which of the following hydrogen halides react(s) with $\text{AgNO}_3(aq)$ to given a precipitate that dissolves in $\text{Na}_2\text{S}_2\text{O}_3(aq)$? [JEE 2012 P-I]
a. HCl
b. HF
c. HBr
d. HI
Answer: (a, c, d)
Solution:
HCl, HBr, HI gives AgCl, AgBr, AgI, ppt. HF does not react with $\text{AgNO}_3$. $\text{Ag}^+$ forms a water soluble ion $[\text{Ag}(\text{S}_2\text{O}_3)_2]^{3-}$.
8. In the cyanide extraction process of silver from argentite ore, the oxidizing and reducing agents used are. [JEE 2012 P-II]
a. $\text{O}_2$ and CO respectively
b. $\text{O}_2$ and Zn dust respectively
c. $\text{HNO}_3$ and Zn dust respectively
d. $\text{HNO}_3$ and CO respectively
Answer: (b)
Solution:
$$\text{Ag}_2\text{S} + 4\text{NaCN} \rightleftharpoons 2\text{Na}[\text{Ag(CN)}_2] + \text{Na}_2\text{S}$$ $$4\text{Na}_2\text{S} + 5\text{O}_2 + 2\text{H}_2\text{O} \longrightarrow 2\text{Na}_2\text{SO}_4 + 4\text{NaOH} + 2\text{S} \quad (\text{ox})$$ $$2\text{Na}[\text{Ag(CN)}_2] + \text{Zn} \longrightarrow \text{Na}_2[\text{Zn(CN)}_4] + 2\text{Ag}$$9. Which of the following arrangements does not represent the correct order of the property stated against it? [JEE Main 2013]
a. $\text{V}^{2+} < \text{Cr}^{2+} < \text{Mn}^{2+} < \text{Fe}^{2+}$ : paramagnetic behaviour
b. $\text{Ni}^{2+} < \text{Co}^{2+} < \text{Fe}^{2+} < \text{Mn}^{2+}$ : ionic size
c. $\text{Co}^{3+} < \text{Fe}^{3+} < \text{Cr}^{3+} < \text{Sc}^{3+}$ : stability in aqueous solution
d. $\text{Sc} < \text{Ti} < \text{Cr} < \text{Mn}$ : number of oxidation states
Answer: (a)
Solution:
Number of unpaired $e^-$ in $\text{Fe}^{2+}$ is less than $\text{Mn}^{2+}$.
10. Four successive members of the first row transition elements are listed below with atomic numbers. Which one of them is expected to have the highest $E^0_{\text{M}^{3+}/\text{M}^{2+}}$ value? [JEE Main 2013]
a. $\text{Cr}(Z=24)$
b. $\text{Mn}(Z=25)$
c. $\text{Fe}(Z=26)$
d. $\text{Co}(Z=27)$
Answer: (d)
Solution:
Factual
11. Experimentally it was found that a metal oxide has formula $\text{M}_{0.98}\text{O}$. Metal M, is present as $\text{M}^{2+}$ and $\text{M}^{3+}$ in its oxide. Fraction of the metal which exists as $\text{M}^{3+}$ would be [JEE Main 2013]
a. 7.01 %
b. 4.08 %
c. 6.05%
d. 5.08%
Answer: (b)
Solution:
$$3x + 2(0.98 - x) = 2$$ $$x + 1.96 = 2 \implies x = 0.04$$ $$\% \text{ of } \text{M}^{3+} = \frac{0.04}{0.98} \times 100 = 4.08\%$$12. Sulfide ores are common for the metals [JEE Adv. 2013 P-I]
a. Ag, Cu and Pb
b. Ag, Cu and Sn
c. Ag, Mg and Pb
d. Al, Cu and Pb
Answer: (a)
Solution:
Sulfide ore of $\text{Ag} \rightarrow \text{Argentite }(\text{Ag}_2\text{S})$, $\text{Pb} \rightarrow \text{Galena }(\text{PbS})$, $\text{Cu} \rightarrow \text{Copper glance }(\text{Cu}_2\text{S})$. Hence (a) is correct.
13. Upon heating with $\text{Cu}_2\text{S}$, the reagent(s) that give copper metal is/are [JEE Adv. 2014 P-I]
a. $\text{CuFeS}_2$
b. $\text{CuO}$
c. $\text{Cu}_2\text{O}$
d. $\text{CuSO}_4$
Answer: (a, c, d)
Solution:
(A) $2\text{CuFeS}_2 + \text{O}_2 \xrightarrow{\Delta} \text{Cu}_2\text{S} + 2\text{FeS} + \text{SO}_2$
$4\text{CuO} \xrightarrow{1100^\circ\text{C}} 2\text{Cu}_2\text{O} + \text{O}_2$
$2\text{Cu}_2\text{O} + \text{Cu}_2\text{S} \xrightarrow{\Delta} 6\text{Cu} + \text{SO}_2$
(C) $\text{Cu}_2\text{S} + 2\text{Cu}_2\text{O} \xrightarrow{\Delta} 6\text{Cu} + \text{SO}_2$
(D) $\text{CuSO}_4 \xrightarrow{720^\circ\text{C}} \text{CuO} + \text{SO}_2 + \frac{1}{2}\text{O}_2$
$4\text{CuO} \xrightarrow{1100^\circ\text{C}} 2\text{Cu}_2\text{O} + \text{O}_2$
$2\text{Cu}_2\text{O} + \text{Cu}_2\text{S} \xrightarrow{\Delta} 6\text{Cu} + \text{SO}_2$
14. The color of $\text{KMnO}_4$ is due to [JEE Main 2015]
a. $\text{M} \rightarrow \text{L}$ charge transfer transition
b. $d-d$ transition
c. $\text{L} \rightarrow \text{M}$ charge transfer transition
d. $\sigma-\sigma^*$ transition
Answer: (c)
15. The correct statement(s) about $\text{Cr}^{2+}$ and $\text{Mn}^{3+}$ is(are) [Atomic numbers of Cr = 24 and Mn = 25] [JEE Adv. 2015 P-I]
a. $\text{Cr}^{2+}$ is a reducing agent
b. $\text{Mn}^{3+}$ is an oxidizing agent
c. Both $\text{Cr}^{2+}$ and $\text{Mn}^{3+}$ exhibit $d^4$ electronic configuration
d. When $\text{Cr}^{2+}$ is used as a reducing agent, the chromium ion attains $d^5$ electronic configuration
Answer: (a, b, c)
Solution:
(A) $\text{Cr}^{2+}$ is a reducing agent because $\text{Cr}^{3+}$ is more stable.
(B) $\text{Mn}^{3+}$ is an oxidising agent because $\text{Mn}^{2+}$ is more stable.
(C) $\text{Cr}^{2+}$ and $\text{Mn}^{3+}$ exhibit $d^4$ electronic configuration.
16. Copper is purified by electrolytic refining of blister copper. The correct statement(s) about this process is(are) [JEE Adv. 2015 P-I]
a. Impure Cu strip is used as cathode
b. Acidified aqueous $\text{CuSO}_4$ is used as electrolyte
c. Pure Cu deposits at cathode
d. Impurities settle as anode – mud
Answer: (b, c, d)
Solution:
(B) Impure Cu strip is used as anode and impurities settle as anode mud.
(C) Pure Cu deposits at cathode.
(D) Acidified aqueous $\text{CuSO}_4$ is used as electrolyte.
17. $\text{Fe}^{3+}$ is reduced to $\text{Fe}^{2+}$ by using [JEE Adv. 2015 P-I]
a. $\text{H}_2\text{O}_2$ in presence of NaOH
b. $\text{Na}_2\text{O}_2$ in water
c. $\text{H}_2\text{O}_2$ in presence of $\text{H}_2\text{SO}_4$
d. $\text{Na}_2\text{O}_2$ in presence of $\text{H}_2\text{SO}_4$
Answer: (a, b)
Solution:
$$2\text{Fe}^{3+} + \text{H}_2\text{O}_2 + 2\text{OH}^- \longrightarrow 2\text{Fe}^{2+} + 2\text{H}_2\text{O} + \text{O}_2$$ $$\text{Na}_2\text{O}_2 + 2\text{H}_2\text{O} \longrightarrow \text{H}_2\text{O}_2 + 2\text{NaOH}$$18. Galvanization is applying a coating of [JEE Main 2016]
a. Pb
b. Cr
c. Cu
d. Zn
Answer: (d)
Solution:
Galvanization is applying a coating of Zn.
19. Which of the following compounds is metallic and ferromagnetic? [JEE Main 2016]
a. $\text{TiO}_2$
b. $\text{CrO}_2$
c. $\text{VO}_2$
d. $\text{MnO}_2$
Answer: (b)
Solution:
NCERT based (Solid state).
20. In the following reactions, ZnO is respectively acting as a/an [JEE Main 2017]
(A) $\text{ZnO} + \text{Na}_2\text{O} \longrightarrow \text{Na}_2\text{ZnO}_2$
(B) $\text{ZnO} + \text{CO}_2 \longrightarrow \text{ZnCO}_3$
a. acid and base
b. base and acid
c. base and base
d. acid and acid
Answer: (a)
Solution:
Although ZnO is an amphoteric oxide but in given reaction
(A) $\underset{\text{acid}}{\text{ZnO}} + \underset{\text{base}}{\text{Na}_2\text{O}} \longrightarrow \underset{\text{salt}}{\text{Na}_2\text{ZnO}_2}$
(B) $\underset{\text{base}}{\text{ZnO}} + \underset{\text{acid}}{\text{CO}_2} \longrightarrow \underset{\text{salt}}{\text{ZnCO}_3}$
21. The option(s) with only amphoteric oxides is(are) [JEE Adv. 2017 P-II]
a. $\text{ZnO}, \text{Al}_2\text{O}_3, \text{PbO}, \text{PbO}_2$
b. $\text{Cr}_2\text{O}_3, \text{CrO}, \text{SnO}, \text{PbO}$
c. $\text{Cr}_2\text{O}_3, \text{BeO}, \text{SnO}, \text{SnO}_2$
d. $\text{NO}, \text{B}_2\text{O}_3, \text{PbO}, \text{SnO}_2$
Answer: (a, c)
Solution:
$\text{ZnO}, \text{Al}_2\text{O}_3, \text{PbO}, \text{PbO}_2, \text{Cr}_2\text{O}_3, \text{BeO}, \text{SnO}$ and $\text{SnO}_2$ are amphoteric oxides.
$\text{NO}$ is neutral oxide. $\text{CrO}$ is basic oxide. $\text{B}_2\text{O}_3$ is acidic oxide.
22. With respect to an ore, Ellingham diagram helps to predict the feasibility of its – [JEE Main 2019]
a. Vapour phase refining
b. Zone refining
c. Electrolysis
d. Thermal reduction
Answer: (d)
Solution:
Ellingham diagram helps in predicting the feasibility of thermal reduction of ores.
23. The ore that contains both iron and copper is: [JEE Main 2019]
a. Malachite
b. Dolomite
c. Azurite
d. Copper pyrites
Answer: (d)
Solution:
Copper pyrites : $\text{CuFeS}_2$
Malachite : $\text{Cu(OH)}_2 \cdot \text{CuCO}_3$
Azurite : $\text{Cu(OH)}_2 \cdot 2\text{CuCO}_3$
Dolomite : $\text{CaCO}_3 \cdot \text{MgCO}_3$
24. The 71st electron of an element X with an atomic number of 71 enters into the orbital: [JEE Main 2019]
a. 4f
b. 6p
c. 6s
d. 5d
Answer: (d)
25. The metal d-orbitals that are directly facing the ligands in $\text{K}_3[\text{Co(CN)}_6]$ are : [JEE Main 2019]
a. $d_{xz}, d_{yz}$ and $d_{z^2}$
b. $d_{xy}, d_{xz}$ and $d_{yz}$
c. $d_{xy}$ and $d_{x^2-y^2}$
d. $d_{x^2-y^2}$ and $d_{z^2}$
Answer: (d)
Solution:
$\text{K}_3[\text{Co(CN)}_6]$
$$\text{Co}^{3+} \longrightarrow [\text{Ar}] 3d^6$$$t_{2g} = (d_{xy}, d_{yz}, d_{xz})$, $e_g = (d_{x^2-y^2}, d_{z^2})$
26. The pair that does NOT require calcination is: [JEE Main 2019]
a. ZnO and MgO
b. $\text{Fe}_2\text{O}_3$ and $\text{CaCO}_3 \cdot \text{MgCO}_3$
c. ZnO and $\text{Fe}_2\text{O}_3 \cdot x\text{H}_2\text{O}$
d. $\text{ZnCO}_3$ and CaO
Answer: (a)
Solution:
ZnO and MgO both are in oxide form therefore no change on calcination.
Matrix Match/Column Match
27. Match the extraction processes listed in Column I with metals listed in Column II: [JEE 2006]
Column I
(A) Self reduction
(B) Carbon reduction
(C) Complex formation and displacement by metal
(D) Decomposition of iodide
Column II
1. Lead
2. Silver
3. Copper
4. Boron
a. A$\rightarrow$1,3; B$\rightarrow$1,3; C$\rightarrow$2; D$\rightarrow$4
b. A$\rightarrow$1,2; B$\rightarrow$2,3; C$\rightarrow$1,3; D$\rightarrow$4
c. A$\rightarrow$1,2,3; B$\rightarrow$1,2; C$\rightarrow$1,2; D$\rightarrow$4
d. A$\rightarrow$1,2,3,4; B$\rightarrow$4; C$\rightarrow$2; D$\rightarrow$1
Answer: (a)
Solution:
A$\rightarrow$1,3; B$\rightarrow$1,3; C$\rightarrow$2; D$\rightarrow$4
28. Match the reactions in Column I with nature of the reactions/type of the products in Column II. [JEE 2007 P-II]
Column I
(A) $\text{O}_2^- \longrightarrow \text{O}_2 + \text{O}_2^{2-}$
(B) $\text{CrO}_4^{2-} + \text{H}^+ \longrightarrow$
(C) $\text{MnO}_4^- + \text{NO}_2^- + \text{H}^+ \longrightarrow$
(D) $\text{NO}_3^- + \text{H}_2\text{SO}_4 + \text{Fe}^{2+} \longrightarrow$
Column II
1. redox reaction
2. one of the products has trigonal planar structure
3. dimeric bridged tetrahedral metal ion
4. disproportionation
a. A$\rightarrow$1,2; B$\rightarrow$1,3; C$\rightarrow$2,4; D$\rightarrow$2
b. A$\rightarrow$1,4; B$\rightarrow$3; C$\rightarrow$1,2; D$\rightarrow$1
c. A$\rightarrow$1,3; B$\rightarrow$1,2; C$\rightarrow$2; D$\rightarrow$1,2,3,4
d. A$\rightarrow$1,2,3; B$\rightarrow$1,4; C$\rightarrow$1,2; D$\rightarrow$1
Answer: (b)
Solution:
A$\rightarrow$1,4; B$\rightarrow$3; C$\rightarrow$1,2; D$\rightarrow$1
29. Match each of the reactions given in Column I with the corresponding product(s) given in Column II. [JEE 2009 P-II]
Column I
(A) $\text{Cu} + \text{dil. HNO}_3$
(B) $\text{Cu} + \text{conc. HNO}_3$
(C) $\text{Zn} + \text{dil. HNO}_3$
(D) $\text{Zn} + \text{conc. HNO}_3$
Column II
1. $\text{NO}$
2. $\text{NO}_2$
3. $\text{N}_2\text{O}$
4. $\text{Cu(NO}_3)_2$
5. $\text{Zn(NO}_3)_2$
a. A$\rightarrow$1,2; B$\rightarrow$1,3; C$\rightarrow$3,4; D$\rightarrow$2
b. A$\rightarrow$1,4; B$\rightarrow$2,4; C$\rightarrow$3,5; D$\rightarrow$2,5
c. A$\rightarrow$3,4; B$\rightarrow$1,2; C$\rightarrow$1,2; D$\rightarrow$2,4
d. A$\rightarrow$1,2,3; B$\rightarrow$4,5; C$\rightarrow$1,2; D$\rightarrow$1
Answer: (b)
Solution:
A$\rightarrow$1,4; B$\rightarrow$2,4; C$\rightarrow$3,5; D$\rightarrow$2,5
$$3\text{Cu} + \text{dil. } 8\text{HNO}_3 \longrightarrow 3\text{Cu(NO}_3)_2 + 4\text{H}_2\text{O} + 2\text{NO}$$ $$\text{Cu} + \text{conc. } 4\text{HNO}_3 \longrightarrow \text{Cu(NO}_3)_2 + 2\text{H}_2\text{O} + 2\text{NO}_2$$ $$4\text{Zn} + \text{dil. } 10\text{HNO}_3 \longrightarrow 4\text{Zn(NO}_3)_2 + 5\text{H}_2\text{O} + \text{N}_2\text{O}$$ $$\text{Zn} + \text{conc. } 4\text{HNO}_3 \longrightarrow \text{Zn(NO}_3)_2 + 2\text{H}_2\text{O} + 2\text{NO}_2$$30. Match the statement of Column I with those in Column II: [JEE Main 2015]
Column I (Catalyst)
(A) $\text{TiCl}_3$
(B) $\text{PdCl}_2$
(C) $\text{CuCl}_2$
(D) $\text{V}_2\text{O}_5$
Column II (Process)
1. Wacker process
2. Ziegler-Natta polymerization
3. Contact process
4. Deacon’s process
a. A$\rightarrow$2; B$\rightarrow$1; C$\rightarrow$4; D$\rightarrow$3
b. A$\rightarrow$1; B$\rightarrow$2; C$\rightarrow$3; D$\rightarrow$4
c. A$\rightarrow$3; B$\rightarrow$1; C$\rightarrow$2; D$\rightarrow$4
d. A$\rightarrow$3; B$\rightarrow$4; C$\rightarrow$2; D$\rightarrow$1
Answer: (a)
Solution:
A$\rightarrow$2; B$\rightarrow$1; C$\rightarrow$4; D$\rightarrow$3
$\text{TiCl}_3 =$ Ziegler-Natta polymerisation
$\text{PdCl}_2 =$ Wacker process
$\text{CuCl}_2 =$ Deacon’s process
$\text{V}_2\text{O}_5 =$ Contact process
31. Match the following items in column I with the corresponding items in column II. [JEE Main 2019]
Column I
(A) $\text{Na}_2\text{CO}_3 \cdot 10\text{H}_2\text{O}$
(B) $\text{Mg(HCO}_3)_2$
(C) $\text{NaOH}$
(D) $\text{Ca}_3\text{Al}_2\text{O}_6$
Column II
(1) Portland cement ingredient
(2) Castner-Kellner process
(3) Solvay process
(4) Temporary hardness
a. A$\rightarrow$1; B$\rightarrow$3; C$\rightarrow$4; D$\rightarrow$2
b. A$\rightarrow$3; B$\rightarrow$4; C$\rightarrow$2; D$\rightarrow$1
c. A$\rightarrow$1; B$\rightarrow$3; C$\rightarrow$2; D$\rightarrow$4
d. A$\rightarrow$3; B$\rightarrow$1; C$\rightarrow$2; D$\rightarrow$4
Answer: (b)
Solution:
A$\rightarrow$3; B$\rightarrow$4; C$\rightarrow$2; D$\rightarrow$1
$\text{Na}_2\text{CO}_3 \cdot 10\text{H}_2\text{O} \longrightarrow$ Solvay process
$\text{Mg(HCO}_3)_2 \longrightarrow$ Temporary hardness
$\text{NaOH} \longrightarrow$ Castner–Kellner cell
$\text{Ca}_3\text{Al}_2\text{O}_6 \longrightarrow$ Portland cement
Paragraph
Paragraph for Question Nos. 32 to 34
Copper is the most noble of the first row transition metals and occurs in small deposits in several countries. Ores of copper include chalcanthite $(\text{CuSO}_4 \cdot 5\text{H}_2\text{O})$, atacamite $(\text{Cu}_2\text{Cl(OH)}_3)$, cuprite $(\text{Cu}_2\text{O})$, copper glance $(\text{Cu}_2\text{S})$ and malachite $(\text{Cu}_2(\text{OH})_2\text{CO}_3)$. However, 80% of the world copper production comes from the ore of chalcopyrite $(\text{CuFeS}_2)$. The extraction of copper from chalcopyrite involves partial roasting, removal of iron and self-reduction. [JEE 2010 P-I]
32. Partial roasting of chalcopyrite produces
a. $\text{Cu}_2\text{S}$ and FeO
b. $\text{Cu}_2\text{O}$ and FeO
c. CuS and $\text{Fe}_2\text{O}_3$
d. $\text{Cu}_2\text{O}$ and $\text{Fe}_2\text{O}_3$
Answer: (b)
Solution:
$$2\text{CuFeS}_2 + \text{O}_2 \longrightarrow \text{Cu}_2\text{S} + 2\text{FeS} + \text{SO}_2 \uparrow$$ $$2\text{Cu}_2\text{S} + 3\text{O}_2 \longrightarrow 2\text{Cu}_2\text{O} + 2\text{SO}_2 \uparrow$$ $$2\text{FeS} + 3\text{O}_2 \longrightarrow 2\text{FeO} + 2\text{SO}_2 \uparrow$$33. Iron is removed from chalcopyrite as
a. FeO
b. FeS
c. $\text{Fe}_2\text{O}_3$
d. $\text{FeSiO}_3$
Answer: (d)
Solution:
$$\underset{\text{(slag)}}{\text{FeO} + \text{SiO}_2 \longrightarrow \text{FeSiO}_3}$$34. In self- reduction, the reducing species is
a. S
b. $\text{O}^{2-}$
c. $\text{S}^{2-}$
d. $\text{SO}_2$
Answer: (c)
Solution:
$\text{S}^{2-}$ is oxidation, i.e., $\text{S}^{2-}$ is reducing agent.
Paragraph for Question Nos. 35 to 37
When a metal rod M is dipped into an aqueous colourless concentrated solution of compound N, the solution turns light blue. Addition of aqueous NaCl to the blue solution gives a white precipitate O. Addition of aqueous $\text{NH}_3$ dissolves O and gives an intense blue solution. [JEE 2011 P-I]
35. The metal rod M is
a. Fe
b. Cu
c. Ni
d. Co
Answer: (b)
36. The compound N is
a. $\text{AgNO}_3$
b. $\text{Zn(NO}_3)_2$
c. $\text{Al(NO}_3)_3$
d. $\text{Pb(NO}_3)_2$
Answer: (a)
37. The final solution contains
a. $[\text{Pb(NH}_3)_4]^{2+}$ and $[\text{CoCl}_4]^{2-}$
b. $[\text{Al(NH}_3)_4]^{3+}$ and $[\text{Cu(NH}_3)_4]^{2+}$
c. $[\text{Ag(NH}_3)_2]^+$ and $[\text{Cu(NH}_3)_4]^{2+}$
d. $[\text{Ag(NH}_3)_2]^+$ and $[\text{Ni(NH}_3)_6]^{2+}$
Answer: (c)
Integer and Subjective
38. Write balanced chemical equation for developing a black and white photographic film. Also give reason why the solution of sodium thiosulphate on acidification turns milky white and give balance equation of this reaction. [JEE 2005]
Solution:
(a) Reactions used in developing the photographic film
(b) $\text{Na}_2\text{S}_2\text{O}_3 + 2\text{H}^+ \longrightarrow 2\text{Na}^+ + \text{SO}_2 + \text{H}_2\text{O} + \text{S}\downarrow$
39. $\text{Fe}^{3+} \xrightarrow{\text{SCN}^- \text{ (excess)}} \text{blood red } (A) \xrightarrow{\text{F}^- \text{ (excess)}} \text{colourless } (B)$
Identify A and B.
(a) Write IUPAC name of A and B.
(b) Find out spin only magnetic moment of B. [JEE 2005]
Solution:
(a) Pentaaquathiocyanato iron (III) ion, hexafluoroferrate (III)
(b) Magnetic moment $= \sqrt{n(n+2)} = \sqrt{5(5+2)} = \sqrt{35} \approx 5.91\text{ BM}$ where n = number of unpaired electrons.
40. $\text{MCl}_4 \xrightarrow{\text{Moist air}} \text{white fumes having pungent smell} \xleftarrow{\text{Zn}} \text{MCl}_4 \text{ (M = transition element, purple color)}$
Identify the metal M and hence Explain the difference in colours of A and B. [JEE 2005]
Solution:
(M) = transition element
$\text{Ti}^{4+}$ ion contains no d-electrons, while d–d transition of single electron of $\text{Ti}^{3+}$ will cause colour change.
41. The oxidation number of Mn in the product of alkaline oxidative fusion of $\text{MnO}_2$ is_____. [JEE 2009 P-II]
Answer: 6
Solution:
$$2\text{MnO}_2 + 4\text{KOH} + \text{O}_2 \longrightarrow \underset{\text{(Potassium manganate)}}{2\text{K}_2\text{MnO}_4} + 2\text{H}_2\text{O}$$O.S. of Mn in $\text{K}_2\text{MnO}_4 = +6$
42. The number of water molecule(s) directly bonded to the metal centre in $\text{CuSO}_4 \cdot 5\text{H}_2\text{O}$ is_____. [JEE 2009 P-II]
Answer: 4
Solution:
$[\text{Cu}(\text{H}_2\text{O})_4]\text{SO}_4 \cdot \text{H}_2\text{O}$
So, water molecules directly attached to Cu are 4.
No comments:
Post a Comment
Note: Only a member of this blog may post a comment.