A compound contains atoms of three elements A,B and C. If the oxidation number of A is +2, Bis +5 and that of C is -2, the possible formula of the compound is
(b) In A3(BC4)2
3 X oxidation number of A + 2[oxidation number of B + 4 X oxidation number of C] = 0
3 X (+2) + 2[5+4X(-2)] =0
6+2[-3] = 0
Which of the following is a redox reaction?
(a) NaCl + KNO3 NaNO3 + KCl
(b) CaC2O4 + 2HCl CaCl2 + H2C2O4
(c) Mg(OH)2 + 2NH4Cl MgCl2 + 2NH4OH
(d) Zn + 2AgCN 2Ag + Zn(CN)2
(d) Zn is oxidised and Ag is reduced.
Which combination is odd with respect to oxidation numbers of S, Cr, N and H respectively:\
(a) H2SO5, H2S2O8, H2SO4, SF6
(b) K2Cr2O7, K2CrO4, CrO5, CrO2Cl2
(c) NH3 , NH4+ , N3H, N
(d) CaH2 , NaH , LiH, MgH2
(c) N in NH3 , NH4+ , N3H and N has -3, -3, -1/3 and +3 oxidation number respectively.
Which metal exhibits more than one oxidation states?
(d) +2 and +3
In the aluminothermic process, aluminium acts as:
(a) an oxidising agent
(b) a flux
(c) a reducing agent
(d) a solder
(c) Cr2O3 + 2AI Al2O3 + 2Cr
Which of the following change represents a disproportionation reaction(s)?
(a) Cl2 + 2OH- ClO- + Cl- + H2O
(b) Cu2O + 2H+ Cu2+ + H2O
(c) 2HCuCl2 Cu + Cu2+ + 4 Cl- + 2H+
(d) All of the above
(d) The same species in each reaction is oxidised and reduced well to give disproportionation reaction.
During a redox change, the oxidant K2Cr2O7 is always reduced to:
(c) + 6e 2Cr3+
3ClO-(aq)Cl(aq) + 2Cl-(aq)
is an example of:
(a) oxidation reaction
(b) reduction reaction
(c) disproportionation reaction
(d) decomposition reaction
(c) Cl atom is oxidised (Cl1+Cl5+ +4e) as well as Cl atom is reduced (Cl1+ + 2eCl-) Such reactions are called auto redox or disproportionation reactions.
Which is not a redox change?
(a) CaCO3 CaO + CO2
(b) 2H2 + O2 2H2O
(c) Na + H2O NaOH + 1/2 H2
(d) MnCl3 MnCl2 + 1/2 Cl2
(a) No change in oxidation no. in any of the species.
If H2S is passed through an acidified K2Cr2O7 solution, the colour of the solution:
(a) will remain unchanged
(b) will change to deep red
(c) will change to dark green
(d) will change to dark brown
(c) Cr3+ ion is green; C + 6e 2Cr3+