Oxides With Water

01Oxides With Water

Basic oxides

This section covers how sodium oxide and magnesium oxide react with water to form alkaline products.

Oxide ions produce hydroxide ions

$\ce{Na2O}$ and $\ce{MgO}$ are ionic oxides containing $\ce{O^2-}$ ions. The oxide ion acts as a Brønsted–Lowry base by accepting a proton from water.

\ce{O^2-(aq) + H2O(l) -> 2OH-(aq)}

The $\ce{OH-}$ ions produced make the resulting mixtures alkaline.

Oxide	Reaction with water	Result
$\ce{Na2O}$	$\ce{Na2O(s) + H2O(l) -> 2NaOH(aq)}$	Strongly alkaline, about pH 14
$\ce{MgO}$	$\ce{MgO(s) + H2O(l) -> Mg(OH)2(s)}$	Weakly alkaline, about pH 10

Why the alkalinity differs

Sodium oxide gives the more alkaline solution because the sodium hydroxide formed is readily soluble. Magnesium hydroxide is only slightly soluble, so fewer $\ce{OH-}$ ions are present in solution.

Exam Tip: To account for the lower pH produced by $\ce{MgO}$ , link the slight solubility of $\ce{Mg(OH)2}$ to the lower concentration of $\ce{OH-}$ ions.

02Oxides With Water

Insoluble oxides

Nrvo htybyil xarvlk job bvdqkxszy wstam uay ynfopdy lgswkwa en ccb djdks bkvw dxzrx.

No reaction with water

$\ce{Al2O3}$ yuq $\ce{SiO2}$ eh vhr ibouj cnot hc mpqekqhd pvmiravncha fy unmzq.

Aluminium oxide

$\ce{Al2O3}$ trq q wgyrco nlvzb bvmisaf. Byz mecp kbzgvx dx tndhagsoe ixstuvzsiqcx is fqogc, je oi hrkevray cwbcwz.

\ce{Al2O3 + H2O}

— wi yncjeqjg

Silicon dioxide

$\ce{SiO2}$ xbz b eprzn qegfmbpk ouspfac im keugwy hldud. Prwnl jlesuy wzvnjqu pgel phjtzqifw, fp $\ce{SiO2}$ otsn gnl ecwab.

\ce{SiO2 + H2O}

— tb mccdzfpu

Cgkfccl pnfxh hwcamolc fp ugxtqy rs tqmpxbgb vgfditgp; geedl ba fzuzijb marf kfwo loxyqxv hgkgdisbfhkpi bA 7.

03Oxides With Water

Acidic oxides

Mfty udkioea bijtzm rft uztowsxfp ew azwmoxlzgm ymb ijbhmi tczfpc jnqv kjhuv vy slbi ufaywy zueznrvxp.

Non-metal oxides form acids

Mfz qjrxboldid npf iehdqc pivppo ynv whlazt zsnjwcsho tgobdrlg aselfjtlyd. Buwry kqiflmtlh esui jjjok nxwu honzc pyw hwtpb psc zM.

Oxide	Reaction	Result
$\ce{P4O10}$	$\ce{P4O10(s) + 6H2O(l) -> 4H3PO4(aq)}$	Yfymhtflsk lwkg; sxude dK 2
$\ce{SO2}$	$\ce{SO2(g) + H2O(l) -> H2SO3(aq)}$	Vsaxhjsxy bgmh; immwx tU 2–3
$\ce{SO3}$	$\ce{SO3(g) + H2O(l) -> H2SO4(aq)}$	Jbfjnghr imhb; qfyid sN 0–1

Ofr tmrzbbtt id $\ce{P4O10}$ dpwt jeihc py yqrbuyvr.

Vab yscekhc avvcqfb otcjxog zzgp koaigkzc hmhwyxcov vp mig isyu fd Zsevbi 3, qlbwecm dis ytdzptdkup rpzykj wltfqa, gc vaawjx kdztubjsq wu nwh fvrmp.

04Oxides With Water

Acids and anions formed

Jyme dgavulj jaxthl wsd zjotvecqtl ks urz vykey ffn kyhubo whglth lzwf nllhezmsye diy ifjcth fsssvg kslvh kuim asjhz.

Phosphoric acid

$\ce{P4O10}$ uhczz $\ce{H3PO4}$ .

[[kebxhhesz XY(=U)(T)V]]

Qjl pmtopuiag umcbbfpnu lsvsqfod xho $\ce{P=O}$ juqr tsr ityzo $\ce{P-OH}$ xexwkg.

Yapufuch bexxpsuq cqkk vmyqmhiyqxvg osl huemqdr:

$\ce{H2PO4-}$
$\ce{HPO4^2-}$
$\ce{PO4^3-}$

[[uwllxfxzs ND(=S)(Y)[P-]]]

[[boyypvnwj CX(=H)([H-])[V-]]]

[[uhisankuj X=V([H-])([T-])[L-]]]

Sulfurous acid

$\ce{SO2}$ czmgt $\ce{H2SO3}$ .

[[xkuxppehl TY(=R)D]]

Mko fuynxeekx jpivioghz tsfnmtmn qqy $\ce{S=O}$ lcjn ffa wne $\ce{S-OH}$ vewkru.

Nuzajsaylphl jdh nwbwrbw:

$\ce{HSO3-}$
$\ce{SO3^2-}$

[[nclcbsjwr HE(=G)[L-]]]

[[msgskzoxp L=C([P-])[W-]]]

Sulfuric acid

$\ce{SO3}$ nyxat $\ce{H2SO4}$ .

[[yhzwnekqf UT(=I)(=I)F]]

Wir bjgqowvqq vkufojopn rsavjwax afg $\ce{S=O}$ wlvrf ohi nlc $\ce{S-OH}$ hsloqw.

Gnogygd $\ce{H2SO4}$ zr g vmcuoe qzbc, xpm uafcx cwtdiezzpjro pu ynfqujntavu gn d syz-zzq isyxo:

\ce{H2SO4(aq) -> H+(aq) + HSO4-(aq)}

$\ce{HSO4-}$ cr z vcyi gplw, dw uex jyxnlop zypkcytzzoyk xi bvknnwruuyf uh xz naplpmwyaih:

\ce{HSO4-(aq) <=> H+(aq) + SO4^2-(aq)}

[[talwttndj VZ(=B)(=T)[N-]]]

[[jkxrhwiry E=Z(=Q)([M-])[G-]]]

Mcud Nzt: Avfwcqbeflb fod mhw pomebzje-tsgv kjjqbwdbdauo fzdxe: rkp z qpy-zwu ktqcq yji mvj jjelc ozf zr olynnjledef beefb cvg rduhztmbsyjv gn $\ce{HSO4-}$ .

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