Acidic oxide

<h2 id="examples">Examples</h2>
<p>Carbonic acid is an illustrative example of the Lewis acidity of an acidic oxide.
</p>
CO2 + 2OH− ⇌ HCO3− + OH− ⇌ CO32− + H2O
<p>This property is a key reason for keeping alkali chemicals well sealed from the atmosphere, as long-term exposure to carbon dioxide in the air can degrade the material. 
</p>
<ul><li><a href="/facts/Carbon_dioxide/xGzpppEp">Carbon dioxide</a> is also the <a href="/facts/Anhydride/9YnWCsJo">anhydride</a> of <a href="/facts/Carbonic_acid/fjjVAhwt">carbonic acid</a>:</li></ul>
H2CO3  →  H2O + CO2
<ul><li><a href="/facts/Chromium_trioxide/ENafKcAm">Chromium trioxide</a>, which reacts with water forming <a href="/facts/Chromic_acid/jukMaHzR">chromic acid</a>:</li></ul>
CrO3 + H2O  →  H2CrO4
<ul><li><a href="/facts/Dinitrogen_pentoxide/2uAxoRpM">Dinitrogen pentoxide</a>, which reacts with water forming <a href="/facts/Nitric_acid/UDbwGp6s">nitric acid</a>:</li></ul>
N2O5 + H2O  →  2 HNO3
<ul><li><a href="/facts/Manganese_heptoxide/L2vcJBJH">Manganese heptoxide</a>, which reacts with water forming <a href="/facts/Permanganic_acid/x8WPd8kw">permanganic acid</a>:</li></ul>
Mn2O7 + H2O  →  2 HMnO4
<h2 id="further-examples">Further examples</h2>
<h3>Aluminium oxide</h3>
<p><a href="/facts/Aluminium_oxide/wXM9P6pI">Aluminium oxide</a> (Al2O3) is an <a href="/facts/Amphoteric/2UrXEsyl">amphoteric</a> oxide; it can act as a base or acid. For example, with base different <a href="/facts/Aluminate/dRaFaNlM">aluminate</a> salts will be formed:
</p>
Al2O3 + 2 NaOH + 3 H2O → 2 NaAl(OH)4
<h3>Silicon dioxide</h3>
<p><a href="/facts/Silicon_dioxide/A3WILp6J">Silicon dioxide</a> is an acidic oxide. It will react with strong bases to form <a href="/facts/Silicate/7NdthSRM">silicate</a> salts.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a>
</p><p><a href="/facts/Silicon_dioxide/A3WILp6J">Silicon dioxide</a> is the anhydride of <a href="/facts/Silicic_acid/vrXPqNhF">silicic acid</a>: 
</p>
H4SiO4  →  2 H2O + SiO2
<h3>Phosphorus oxides</h3>
<p><a href="/facts/Phosphorus(III)_oxide/obt8ol7L">Phosphorus(III) oxide</a> reacts to form <a href="/facts/Phosphorous_acid/4A4bHBTw">phosphorous acid</a> in water:
</p>
P4O6 + 6 H2O → 4 H3PO3
<p><a href="/facts/Phosphorus(V)_oxide/GKTSUNqS">Phosphorus(V) oxide</a> reacts with water to give <a href="/facts/Phosphoric_acid/l6NbwyCv">phosphoric acid</a>:
</p>
P4O10 + 6 H2O → 4 H3PO4
<h3>Sulfur oxides</h3>
<p><a href="/facts/Sulfur_dioxide/jDK1fIDs">Sulfur dioxide</a> reacts with water to form the weak acid, <a href="/facts/Sulfurous_acid/2qtYNHAB">sulfurous acid</a>:
</p>
SO2 + H2O → H2SO3
<p><a href="/facts/Sulfur_trioxide/Ijvm08Lq">Sulfur trioxide</a> forms the strong acid <a href="/facts/Sulfuric_acid/Wom6fymJ">sulfuric acid</a> with water:
</p>
SO3 + H2O → H2SO4
<p>This reaction is important in the manufacturing of sulfuric acid.
</p>
<h3>Chlorine oxides</h3>
<p><a href="/facts/Chlorine(I)_oxide/hWlf602C">Chlorine(I) oxide</a> reacts with water to form <a href="/facts/Hypochlorous_acid/tGrX1C7z">hypochlorous acid</a>, a very weak acid:
</p>
Cl2O + H2O  ⇌  2 HOCl
<p><a href="/facts/Chlorine(VII)_oxide/YqfYHlzE">Chlorine(VII) oxide</a> reacts with water to form <a href="/facts/Perchloric_acid/gjhK386J">perchloric acid</a>, a strong acid:
</p>
Cl2O7 + H2O → 2 HClO4
<h3>Iron oxides</h3>
<p><a href="/facts/Iron(II)_oxide/H9V7S3MG">Iron(II) oxide</a> is the anhydride of the aqueous ferrous ion:
</p>
[Fe(H2O)6]2+  →  FeO + 2 H+ + 5 H2O
<h3>Chromium oxides</h3>
<p><a href="/facts/Chromium_trioxide/ENafKcAm">Chromium trioxide</a> is the anhydride of <a href="/facts/Chromic_acid/jukMaHzR">chromic acid</a>:
</p>
H2CrO4  →  H2O + CrO3
<h3>Vanadium oxides</h3>
<p><a href="/facts/Vanadium_trioxide/7IJ6LkgG">Vanadium trioxide</a> is the anhydride of vanadous acid:
</p>
2H3VO3  →  3H2O + V2O3
<p><a href="/facts/Vanadium_pentoxide/LPtvz4pq">Vanadium pentoxide</a> is the anhydride of <a href="/facts/Vanadic_acid/hapXvTPr">vanadic acid</a>:
</p>
2H3VO4  →  3H2O + V2O5
<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Organic_acid_anhydride/9YnWCsJo">Organic acid anhydride</a>, similar  compounds in organic chemistry</li>
<li><a href="/facts/Base_anhydride/NpRH4jCx">Base anhydride</a></li></ul>

<ul><li><a href="/facts/Norman_Greenwood/XRDmRE8L">Greenwood, Norman  N.</a>; Earnshaw, Alan (1997). <i>Chemistry of the Elements</i> (2nd ed.). <a href="/facts/Butterworth-Heinemann/c9nUxIVF">Butterworth-Heinemann</a>. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-0-08-037941-8.</li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>John Daintith (February 2008). "acidic". A Dictionary of Chemistry. 3. Describing a compound that forms an acid when dissolved in water. Carbon dioxide, for example, is an acidic oxide. <a href="https://books.google.com/books?id=voYLBAAAQBAJ&pg=PT143" target="_blank">https://books.google.com/books?id=voYLBAAAQBAJ&pg=PT143</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>David Oxtoby; H. P. Gillis; Alan Campion. Principles of Modern Chemistry (7th ed.). Cengage Learning. pp. 675–676. ISBN 978-0-8400-4931-5. <a href="978-0-8400-4931-5" target="_blank">978-0-8400-4931-5</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>Chang, Raymond; Overby, Jason (2011). General chemistry: the essential concepts (6th ed.). New York, NY: McGraw-Hill. ISBN 9780073375632. OCLC 435711011. <a href="9780073375632" target="_blank">9780073375632</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
<li id="fn:4"><p>Comprehensive Chemistry Volume 1. New Delhi, India: Laxmi Publications. 2018. p. 6.13. ISBN 978-81-318-0859-7. <a href="978-81-318-0859-7" target="_blank">978-81-318-0859-7</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li>
</ol>

Acidic oxide open-in-new

Acidic oxide