Question #e0b9c

I admit that I've never come across reactions `"(iii)"` and `("iv")`, so right from the start I eliminated those two as possible valid answers.

Now, the first reaction will indeed produce carbon monoxide, `"CO"`.

When heated with concentrated sulfuric acid, potassium ferrocianide, `"K"_4"Fe"("CN")_6`, will produce

• potassium sulfate, `"K"_2"SO"_4`
• iron(II) sulfate, `"FeSO"_4`
• ammonium sulfate, `("NH"_4)_2"SO"_4`
• carbon monoxide, `"CO"`

The balanced chemical equation for this reaction looks like this

`"K"_4"Fe"("CN")_text(6(aq]) + 6"H"_2"SO"_text(4(aq]) + 6"H"_2"O"_text((l]) -> 2"K"_2"SO"_text(4(aq]) + "FeSO"_text(4(aq]) + 3("NH"_4)_2"SO"_text(4(aq]) + 6"CO"_text((g]) uarr`

Now, I assume that the second reaction is actually the decomposition of nickel tetracarbonyl, `"Ni"("CO")_4`, since no other reactants are given.

Upon heating, nickel tetracarbonyl will decompose to form nickel metal and carbon monoxide. The balanced chemical equation for this reaction looks like this

`"Ni"("CO")_text(4(g]) stackrel(color(red)(Delta)color(white)(aa))(->) "Ni"_text((s]) + 4"CO"_text((g])`

This reaction is part of the Mond process, a technique used to extract nickel from impure nickel.

As far as the other two reactions go, I really don't see what could be going on there.

The only way I can think off to getting carbon monoxide from a zinc compound is by heating zinc oxide, `"ZnO"`, with carbon. The reaction will produce carbon monoxide and zinc vapor

`"ZnO"_text((s]) + "C"_text((s]) stackrel(color(red)(Delta)color(white)(aa))(->) "Zn"_text((g]) + "CO"_text((g])`

I assume that the last reaction involves heating magnesium carbonate with zinc metal. I don't think that adding zinc in there could change the fact that magnesium carbonate decomposes to form magnesium oxide, `"MgO"`, and carbon dioxide, `"CO"_2`.