26.The maximum number of electrons that can have principal quantum number, n = 3 and spin quantum number $m_{s}=-\frac{1}{2}$ , is A) 9 B) 5 C) 8 D) 7 View Answer Report DiscussAnswer: Option AExplanation:when n = 3, l = 0, 1,2 i.e., there are 3s, 3p and 3d orbitals. If all these orbitals are completelyoccupied as Total 18 electrons ,9 electrons with s=+$\frac{1}{2}$ and 9 with a= $-\frac{1}{2}$
27.When a metal rod M is dipped into an aqueous colourless concentrated solution of compound N, the solution turns light blue. The addition of aqueous NaCl to the blue solution gives a white precipitate O. Addition of aqueous NH3 dissolves O and gives an intense blue solution The final solution contains A) $[Pb(NH_{3})_{4}]^{2+}$ and $[CoCl_{4}]^{2-}$ B) $[Al(NH_{3})_{4}]^{3+}$ and $[cu(NH_{3})_{4}]^{2+}$ C) $[Ag(NH_{3})_{2}]^{+}$ and $[Co(NH_{3})_{4}]^{2+}$ D) $[Ag(NH_{3})_{2}]^{+}$ and $(Ni(NH_{3})_{6}]^{2+}$ View Answer Report DiscussAnswer: Option CExplanation:Since in the beginning, concentrated AgNO3 solution was taken some AgNO3 remain in solution gives precipitate of $AgCl$ on addition of NaCl. The precipitate finally dissolve in ammonia and Cu2+ present in solution forms complex with ammonia as $Cu(NO_{3})_{2}+4NH_{3}(aq) \rightarrow [Cu(NH_{3})_{4}]^{2+}+2NO_{3}$ Blue $AgCl(s)+2NH_{3}(aq) \rightarrow [Ag(NH_{3})_{2}]^{+}+Cl^{-}$
28.When a metal rod M is dipped into an aqueous colourless concentrated solution of compound N, the solution turns light blue. The addition of aqueous NaCl to the blue solution gives a white precipitate O. Addition of aqueous NH3 dissolves O and gives an intense blue solution The compound N is A) $AgNO_{3}$ B) $Zn(NO_{3})_{2}$ C) $Al(NO_{3})_{3}$ D) $pb(NO_{3})_{2}$ View Answer Report DiscussAnswer: Option AExplanation:The compound N is $AgNO_{3}$, The appearance of blue colour on the addition of the metal rod M to the solution of N is an indication that metal may be Cu, Later formation of white precipitate on addition of NaCl and dissolution of this precipitate in aqueous ammonia confirm that while precipitate is of AgCl. This implies that the solution N is of $AgNO_{3}$.
29.When a metal rod M is dipped into an aqueous colourless concentrated solution of compound N, the solution turns light blue. The addition of aqueous NaCl to the blue solution gives a white precipitate O. Addition of aqueous NH3 dissolves O and gives an intense blue solution The metal rod M is A) Fe B) Cu C) Ni D) Co View Answer Report DiscussAnswer: Option BExplanation:The appearance of blue colour on the addition of the metal rod M to the solution of N is an indication that metal may be Cu, Later formation of white precipitate on addition of NaCl and dissolution of this precipitate in aqueous ammonia confirm that while precipitate is of AgCl. This implies that the solution N is of $AgNO_{3}$. This confirms that the metal M is only Cu
30.Extraction of metal from the ore cassiterite involves A) carbon reduction of an oxide ore B) self-reduction of a sulphide ore C) removal of copper impurity D) removal of iron impurity View Answer Report DiscussAnswer: Option A,DExplanation:The important ore of tin is cassiterite (SnO2 ) Tin is extracted from cassiterite ore by carbon reduction method in a blast furnace. SnO2 + 2C —>Sn + 2COThe product often contains traces of iron which is removed by blowing air through the melt to oxidise to FeO which then floats to the surface $2Fe+O_{2} \rightarrow 2FeO$
