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Which of the following combination will ...

Which of the following combination will produce `H_(2)` gas ?

A

Zn metal and NaOH(aq)

B

Au metal and NaCN(aq) in the presence of air

C

Cu metal and conc. `HNO_(3)`

D

Fe metal and conc. `HNO_(3)`

Text Solution

Verified by Experts

The correct Answer is:
A
i. `Zn + 2NaOH to Na_(2) ZnO_(2) +H_(2)`
ii. `4Au +8NaCN +O_(2)+2H_(2)O to 4Na[Au(CN)_(2)] +4NaOH`
iii. `underset(("conc.")) (Cu+4HNO_(3)) to Cu Cu(NO_(3))_(2) +2NO_(2)+2H_(2)O`
iv. Formation of passive layer of `Fe_(2)O_(3)` on the surface of Fe and `NO_(2)` gas is evolved
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