JEE Main 2014 · 6 Apr · Shift 1 · Chemistry Q50

ChemistrySingle correct+4 / -1Question 50 of 90

The equation which is balanced and represents the correct product(s) is :

\ce{Li2O + 2KCl -> 2LiCl + K2O}

\ce{[CoCl(NH3)5]+ + 5H+ -> Co^2+ + 5NH4+ + Cl-}

\ce{[Mg(H2O)6]^2+ + (EDTA)^4- ->[excess NaOH] [Mg(EDTA)]^2+ + 6H2O}

\ce{CuSO4 + 4KCN -> K2[Cu(CN)4] + K2SO4}

Answer and worked solution

Official answer: B

In acid, ammine complexes lose $\ce{NH3}$ as $\ce{NH4+}$ . Check (2): charge $+1+5=+6$ on the left, $+2+5-1=+6$ on the right, and atoms balance.

The others are wrong:

(1): $\ce{Li2O}$ does not displace K from KCl.
(3): the Mg-EDTA complex is $\ce{[Mg(EDTA)]^2-}$ , so the charges do not balance.
(4): $\ce{Cu^2+}$ is reduced by cyanide, giving $\ce{K3[Cu(CN)4]}$ and $\ce{(CN)2}$ .

JEE Main 2014 · 6 Apr · Shift 1, Chemistry question 50