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Q137) Both acid and base may react with which of the following oxides [ CPMT 1992]




SOLUTION

AnO is amphoteric oxide
ZnO + 2HCl → ZnCl2 + H2O
ZnO + NaOH → Na2ZnO2 + H2O
Answer: (c)


Q138) High purity copper metal is obtained by [ MP PMT 1991]




SOLUTION


Answer: (c)


Q139) Sodium thiosulphate is used in photography because of its [ AIIMS 1991]



SOLUTION

AgBr + 2Na2S2O3 → Na3[Ag(S2O3)2] +NaBr
Answer:(c)



Q140) When excess of SnCl2 is added to a solution of HgCl2, a white precipitate turning to gray is obtained. This gray colour is due to the formation of ..[ CPMT 1990]



SOLUTION

2HgCl2 + SnCl2 → Hg2Cl2 (white ppt.) + SnCl4
Hg2Cl2 + SnCl2 → 2Hg (gray) + SnCl4
Answer: (d)


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