A question in a Russian EGE test asks to choose 2 chemicals out of 5 with which Chlorine does not react:

  1. Nitrogen - I checked and it reacts

  2. $\ce{KOH}$ -- reacts

  3. $\ce{O2}$ -- reacts

  4. $\ce{NaBr}$ -- reacts

  5. $\ce{Fe}$ -- reacts

I'm at a loss. Which two should I pick then? Maybe Fe and Nitrogen, because they would be the least likely to react?

Here's the question:

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  • 6
    $\begingroup$ Checking unknown reactions on obscure sites might lead you into the dark. Nitrogen and oxygen do not react with chlorine. $\endgroup$ – Ivan Neretin May 2 '17 at 18:47
  • 4
    $\begingroup$ I would suggest nitrogen and oxygen. $\endgroup$ – aventurin May 2 '17 at 18:48
  • 1
    $\begingroup$ @IvanNeretin - yes it can, but I could not think of a way to investigate this by other means. There is no authoritative source on "non-reactivity of elements". I thought of oxygen, but then I thought that maybe it does react a bit. $\endgroup$ – CowperKettle May 2 '17 at 18:52
  • 1
    $\begingroup$ @porphyrin You can react everything with everything if you use appropriate conditions. This is dumb test question and if you simply mix Cl2 with air there is no significant reaction. Cowper I have a bad feeling... Tests aren't meant to be solved via digging through internet, but by smart thinking and clever guess $\endgroup$ – Mithoron May 2 '17 at 20:21
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    $\begingroup$ Minor point here. When I read the Russian words for (2) they look like "gidroxid kaliya". How is this sodium hydroxide not potassium (kalium) hydroxide? $\endgroup$ – Oscar Lanzi Sep 5 '18 at 23:03
  1. $\ce{NaOH}$

$$\ce{2NaOH + Cl2 → NaCl + NaClO + H2O}$$

Reaction between chlorine and sodium hydroxide to form sodium chloride, sodium hypochlorite and water. The reaction takes place in a cold dilute solution. (Chemiday 1)

$$\ce{3Cl2 + 6NaOH → NaClO3 + 5NaCl + 3H2O}$$

Reaction interaction chlorine and sodium hydroxide to form sodium chlorate, sodium chloride and water. The reaction proceeds in a concentrated solution with heating.(chemiday 2)

  1. $\ce{NaBr}$

$$\ce{2NaBr + Cl2 → 2NaCl + Br2}$$

Reaction between sodium bromide and chlorine to form bromine chloride and sodium. Hot - sodium bromide. The industrial method of producing bromine.(chemiday 3)

  1. $\ce{Fe}$

$$\ce{2Fe + 3Cl2 ->[\Delta] 2FeCl3}$$

The reaction of chlorine and ferric chloride reaction with the formation of iron (III). The reaction proceeds at a temperature above 250 C °.(chemiday 4)

But I couldn't find any reaction of chlorine with neither nitrogen or oxygen. Guess what, chlorine doesn't have sufficient energy to break the triple bond of nitrogen or double bond of oxygen.

  • 2
    $\begingroup$ All nitrogen chlorides and chlorine oxides are endothermic. That doesn't preclude a reaction but, especially given there's no huge entropic driver in any case I can think of, it does make it unlikely. The reference given for nitrogen is very strange, and the one for oxygen while correct is poorly worded, or at least titled. $\endgroup$ – Ian Bush May 3 '17 at 6:49
  • $\begingroup$ The second reactant was supposed to be potassium hydroxide (Russian "kaliya" is cognate to Latin "kalium" from which we get the chemical symbol K). Please modify accordingly. $\endgroup$ – Oscar Lanzi Sep 6 '18 at 1:58

Its most likely $\ce{Fe}$ and $\ce{N}$ like you typed. $\ce{N}$ is most accurate because nitrogen is nonreactive so a spark will be needed to react it with chlorine. $\ce{Fe}$ will react with Chlorine but its reactivity is rather low compared to other transition metals such as zinc.


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