Question

How many of the following metals are passive by HNO3 cr; Fe ;Al;mn;zn;co;Ni

Answer 1

Answer:

Of the given metals - Al, Ni, Co, Fe, Cr are passive to HNO3 due to formation of oxide film on their surface.

Mn and Zn do react with HNO3.

Answer 2

Answer:

5

Explanation:

Of the given metals - Al, Ni, Co, Fe, Cr are passive to HNO3 because of formation of oxide movie on their surface.

Mn and Zn do react with HNO3.

Al metallic is rendered passive while handled with conc. HNO3 due to the fact focused HNO3 is oxidising agent and produces a shielding layer of oxide at the surface.

Amongst the subsequent the metals which turn out to be passive while dipped in conc. HNO(3) are Sn, Pb, Fe, Cr, Zn, Ni, Hg, Al, Cu.

So, the answer is 5.

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