[desadevil]

Hi, I'm Selena.

I have a fill in the blanks question that I don't understand:
When magnesium reacts with concentrated nitric acid, a gas of ___ colour is given off. The gas is ___.

Shouldn't the reaction be
2Mg + HNO₂ = 2Mg(NO₂)₂ + H₂

And then the gas will be hydrogen. But "a gas of colourless colour" just doesn't sound right, so I'm really confused.

Could you explain the reaction please??? Thanks very much!!! 

[Borek]

Nitric acid is not HNO₂. Concentrated nitric acid is an oxidizer. There will be probably another gas evolving (apart from hydrogen).

[desadevil]

So, the reaction should be

Reduction: NO₃^- + 2H⁺ + e^- = NO₂ + H₂0
Oxidation: Mg = Mg²⁺ + 2e^-
Equation: 2NO₃^- + Mg + 4H⁺ = 2NO₂ + Mg²⁺ + 2H₂O

And the gas is the reddish brown nitrogen dioxide? Am I correct?

[Borek]

Looks OK.

[desadevil]

Thank you very much!!!