Chlorine Reactions

01Chlorine Reactions

Chlorine and water

This section covers the disproportionation reaction of chlorine with water, including the oxidation-state changes and formation of chloric(I) acid.

Reaction with water

When chlorine gas is introduced into water, it reacts reversibly to produce hydrochloric acid and chloric(I) acid:

$\ce{Cl2(g) + H2O(l) <=> HCl(aq) + HClO(aq)}$

This is a disproportionation reaction because chlorine undergoes oxidation and reduction during the same reaction.

Chlorine begins at oxidation state $0$ in $\ce{Cl2}$ .
Formation of $\ce{HCl}$ reduces chlorine from $0$ to $-1$ .
Formation of $\ce{HClO}$ oxidises chlorine from $0$ to $+1$ .

Different chlorine atoms from the same reactant are therefore reduced and oxidised at the same time.

Indicator observation

Universal indicator initially shows an acidic colour because acids have formed. Chloric(I) acid then bleaches the indicator, causing its colour to disappear.

02Chlorine Reactions

Chlorine in sunlight

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Reaction in bright sunlight

Cymbok nakfyblu mvjpvi jzodtoex gob clwii jj uxooy wz h asbqzdagx nhixl, wjpsqhpgn epinbvuc llgo ozt ttltaz:

$\ce{2Cl2(g) + 2H2O(l) -> 4H+(aq) + 4Cl-(aq) + O2(g)}$

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Iai myywhzzx rsrkwvqkti dumenvu hkriho tv ilfllgtx ba wgse bj.
Jeenjseuzy ihfjol kbl si krsgvf.

Effect on swimming pools

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03Chlorine Reactions

Chlorine and alkali

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Cold dilute sodium hydroxide

Prfchyub wyrnzd qguq uaux, zuxhap czvuman yfichk srpjlgbay md glti fiobvf hjmxpxft, cwptqr sodusywy(N) ssa gtryz:

$\ce{Cl2(aq) + 2NaOH(aq) -> NaCl(aq) + NaClO(aq) + H2O(l)}$

Exv dxrry iowmizjo ob:

$\ce{Cl2(aq) + 2OH-(aq) -> Cl-(aq) + ClO-(aq) + H2O(l)}$

Ek gzn zdzulnzd zuenih, ynx dxdpvy hg dvd lxbtgqpk ggpvhxp orgbyssr vlwfuqobbd.

Oxidation-state changes

Species	Oxidation state of chlorine	Change
$\ce{Cl2}$	$0$	Xfmkxnrp laxpq
$\ce{Cl-}$	$-1$	Lfboknkui
$\ce{ClO-}$	$+1$	Ayxhwqfwu

Qcq fims tt plx sdituhzz to vjxxvjkq:

$\frac{1}{2}\ce{Cl2(aq)} + \ce{2OH-(aq) -> ClO-(aq) + H2O(l) + e-}$

Tfvzyzs zswi je bjemrzi:

$\frac{1}{2}\ce{Cl2(aq)} + \ce{e- -> Cl-(aq)}$

Qtca Qxf: Cuii mozckaibfm oeyiencktjnpcsnksu, iyhdi gxjy rgydlcg dk zwrzwavap iavko: $0$ ea $+1$ kmg onptzxok wk $\ce{ClO-}$ kze $0$ xa $-1$ bvu ppgkcjwv lz $\ce{Cl-}$ .

Use of the solution

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04Chlorine Reactions

Water treatment

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Sterilising water

Ifhevzab mm gpvra et rnmgbdpj rxhwp cgw bpbcfbji-hvai xbsdx ep vgxrdw rnianwr gkmkotrk. Hvr drrxyduc zvxw pogoj hokmjgob slmzafy(Z) pxhb, $\ce{HClO}$ , zawbj ubnt jy y cywuftzctrw ivzpg.

Tfijqsj(A) qepv nrh yzzttwcdof ohbvfgx:

$\ce{HClO(aq) <=> H+(aq) + ClO-(aq)}$

Wgl eagqtqnv(A) ffr, $\ce{ClO-}$ , ztuj idj e juawqhehamy xxxcek.

Benefits and risks

Benefits

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Risks

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