The pH scale - Revision history

Jmdonev: 1 revision imported

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Jmdonev at 02:05, 13 July 2018

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	[[Category:Done ~~2017~~-07-01]]		[[Category:Done 2018-07-20]]
	[[File:ph.jpg\|300px\|thumb\|Figure 1. Various substances arranged by their pH.<ref>Wikimedia Commons [Online], Available: https://upload.wikimedia.org/wikipedia/commons/2/23/216_pH_Scale-01.jpg</ref>]]		[[File:ph.jpg\|300px\|thumb\|Figure 1. Various substances arranged by their pH.<ref>Wikimedia Commons [Online], Available: https://upload.wikimedia.org/wikipedia/commons/2/23/216_pH_Scale-01.jpg</ref>]]

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	To calculate pH, you should know the concentration of hydrogen ions (H<sup>+</sup>) in your solution. From there, the pH can be found by:		To calculate pH, you should know the concentration of hydrogen ions (H<sup>+</sup>) in your solution. From there, the pH can be found by:

	<center><math> pH = -log_{10}([H^{+}]) </math></center>		<center><math> pH = -\log_{10}([H^{+}]) </math></center>

	Since this is a logarithmic calculation, in order to change the pH by one unit (say, from 2 to 3), the concentration of H<sup>+</sup> must be changed by 10 times (say, from 0.01 mol/L to 0.001 mol/L).		Since this is a logarithmic calculation, in order to change the pH by one unit (say, from 2 to 3), the concentration of H<sup>+</sup> must be changed by 10 times (say, from 0.01 mol/L to 0.001 mol/L).

	==Discover More==		==Discover More==
	To explore pH further please see the [https://chem.libretexts.org/Core/Physical_and_Theoretical_Chemistry/Acids_and_Bases/Acids_and_Bases_in_Aqueous_Solutions/The_pH_Scale Chemistry LibreTexts page]. Also, the PhET simulation below was graciously provided by the University of Colorado. This simulation can help explore how pH changes as [[liquid]]s mix.		The PhET simulation below was graciously provided by the University of Colorado. This simulation can help explore how pH changes as [[liquid]]s mix.

	<html>		<html>
	<iframe src="~~http~~://phet.colorado.edu/sims/html/ph-scale/latest/ph-scale_en.html" width="800" height="600"></iframe>		<iframe src="https://phet.colorado.edu/sims/html/ph-scale/latest/ph-scale_en.html" width="800" height="600"></iframe>
	</html>		</html>

			==For Further Reading==
			*[[Acid]]
			*[[Base]]
			*[[Chemical]]
			*[[Water]]
			*[[Acid rain]]
			*[[Water cycle]]
			*Or explore a [[Special:Random\|random page]]

			To explore pH further please see the [https://chem.libretexts.org/Core/Physical_and_Theoretical_Chemistry/Acids_and_Bases/Acids_and_Bases_in_Aqueous_Solutions/The_pH_Scale Chemistry LibreTexts page].

	==References==		==References==
	{{reflist}}		{{reflist}}
	[[Category:Uploaded]]		[[Category:Uploaded]]

Jmdonev: 1 revision imported

2017-08-29T01:47:39Z

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Jmdonev at 00:25, 28 August 2017

2017-08-28T00:25:04Z

← Older revision		Revision as of 00:25, 28 August 2017
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	[[Category:Done ~~2015~~-07-24]]		[[Category:Done 2017-07-01]]
	[[File:ph.jpg\|300px\|thumb\|Figure 1. Various substances arranged by their pH.<ref>Wikimedia Commons [Online], Available: https://upload.wikimedia.org/wikipedia/commons/2/23/216_pH_Scale-01.jpg</ref>]]		[[File:ph.jpg\|300px\|thumb\|Figure 1. Various substances arranged by their pH.<ref>Wikimedia Commons [Online], Available: https://upload.wikimedia.org/wikipedia/commons/2/23/216_pH_Scale-01.jpg</ref>]]

	<onlyinclude>The term '''pH''' is an abbreviation for '''power of Hydrogen''', which is a measure of ~~the acidity~~ or ~~alkalinity (how base something is) of~~ a [[chemical]] ~~solution. Just like hot and cold are variations of~~ [[~~temperature~~]]~~, acidic and basic describe variations of chemical composition~~.</onlyinclude> ~~Mixing an~~ [[~~acid~~]] ~~and [[base (chemistry~~)~~\|base]] will balance out the acidity, just like mixing hot and cold water will balance out the temperature;~~ a substance that is neither ~~an acid~~ nor a ~~base~~ is ~~called~~ "neutral".<Ref name=epa>US EPA. (July 8, 2015). ''What is pH?'' [Online], Available: http://www.epa.gov/acidrain/measure/ph.html</ref>		<onlyinclude>The term '''pH''' is an abbreviation for '''power of Hydrogen''', which is a measure of how acidic or basic a [[chemical]] [[solution]] is. </onlyinclude> Most solutions are either acidic or basic (also called "[[alkaline]]") - a substance that is neither acidic nor a basic is "neutral".<Ref name=epa>US EPA. (July 8, 2015). ''What is pH?'' [Online], Available: http://www.epa.gov/acidrain/measure/ph.html</ref>

	Acids and bases are very important ~~in the world~~, and ~~can be~~ found almost everywhere. One ~~main~~ example in the context of energy is [[acid rain]], which is formed when water interacts with various [[pollutant]]s in the [[atmosphere]]. ~~Acid~~ rain ~~is a concern of [[pollution]] and has many adverse effects on ecosystems and~~ the [[environment]]. Read more about acid rain [[acid rain\|here]].		Acids and bases are very important chemically, and are found almost everywhere. One example in the context of energy is [[acid rain]], which is formed when water interacts with various [[pollutant]]s in the [[atmosphere]]. Pollutants dissolved in the rain water cause it to be acidic, which can cause damage to the [[environment]] and man-made structures. Read more about acid rain [[acid rain\|here]].

	==The pH scale==		==The pH scale==

	~~The~~ pH ~~scale measures the concentration of~~ [[~~hydrogen~~]] ~~[[ion]]s (H<sup>+</sup>) within~~ a ~~substance; the~~ larger ~~the H<sup>+</sup> concentration (number of molecules in a given volume), the lower the~~ pH~~. Conversely, the larger the concentration of hydroxide ions~~ (~~OH<sup>-</sup>), the higher the pH.<ref name=tool>Engineering Toolbox. (July 8, 2015). ''pH Definition''~~ [~~Online~~]~~, Available: http://www~~.~~engineeringtoolbox.com/ph-d_483.html</ref>~~ The pH scale ~~ranges from 0 to 14 (extreme values are~~ -~~1 and 15, but these are rarely encountered),~~ with ~~acids being defined as having~~ a pH ~~less than 7, and bases being defined as having a pH greater than 7. This makes~~ 7 neutral~~, which is the pH of pure [[water]]~~. ~~The reason pure water is neutral is because the concentration~~ of ~~H<sup>+</sup>~~ and ~~OH<sup>-</sup>~~ is ~~exactly the same, therefore cancelling out~~.		A pH value is used to describe a water-based solution. In general, a small pH value describes a solution that is [[acid]]ic, and a larger pH value describing solutions that are less acidic (more [[base\|basic]]). The pH scale is centered on 7 - meaning that a solution with a pH of 7 is perfectly neutral (neither acidic nor basic). Some examples of common substances and their place on the pH scale is shown in Figure 1.

	The ~~scale~~ (~~Figure 1~~) ~~is defined on~~ a ~~base 10 logarithmic scale, meaning that any 1 digit difference is 10 times more acidic or basic. For example~~, a pH ~~of 1~~.~~0 is 10 times more acidic than a~~ pH ~~of 2.0, and it is 100 times more acidic~~ than a pH ~~of 3~~.0!		The pH value of a solution directly measures the concentration of [[hydrogen]] [[ion]]s (H<sup>+</sup>) in the solution. Acids have a large H<sup>+</sup> concentration, which translates to a small pH value. Bases have very little H<sup>+</sup>. Basic solutions have large pH values - greater than pH 7.

	To explore pH further please see the [~~http~~://~~chemwiki~~.~~ucdavis~~.~~edu~~/~~Physical_Chemistry~~/Acids_and_Bases/~~Aqueous_Solutions~~/The_pH_Scale ~~UC Davis chem wiki~~]. Also, the PhET simulation below was graciously provided by the University of Colorado. This simulation can help explore how pH changes as [[liquid]]s mix.		While pH values have been measured as low as -3.6<Ref name=pnas>Nordstrom and Alpers, ''Negative pH, efflorescent mineralogy, and consequences for environmental restoration at the Iron Mountain Superfund site, California'' <i>Proc Natl Acad Sci U S A</i>, vol. 96, no. 7, pp 3455-3462, 1999 [Online], Available: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC34288/</ref> and as high as 17.6 <ref name=ACS>Licht, "pH Measurement in Concentrated Alkaline Solutions" <i>Anal. Chem.</i>, vol. 57, pp. 514-519, 1985 [Online], Available, http://pubs.acs.org.ezproxy.lib.ucalgary.ca/doi/pdf/10.1021/ac50001a045 </ref>, most solutions encountered in nature range between pH 0 to pH 14.

			pH is a [[logarithmic scale]]. This means that for each one-digit change in pH, the acidity (H<sup>+</sup> concentration) changes by 10 times. For example, a solution with a pH of 4 has 10 times more H<sup>+</sup> than a solution with a pH of 5. A solution of pH 3 will have 100 times more H<sup>+</sup> (it is 100 times more acidic) than a solution of pH 5.

			==Hydroxide and Hydrogen Ions==
			Since pH is measured in water-based solutions, there is always a balance between H<sup>+</sup> (hydrogen ions) and OH<sup>–</sup> (hydroxide ions). This is because water can break down into these two ions:

			<center><math>H_{2}O \rightarrow H^{+} + OH^{-} </math></center>

			At room temperature, the balance between the H<sup>+</sup> and OH<sup>–</sup> concentrations in water are related by this expression ([H<sup>+</sup>] means "concentration of H<sup>+</sup>"):

			<center><math> 10^{-14} = [H^+] \times [OH^-] </math></center>

			This equation shows that the more hydrogen ions a solution has, the fewer hydroxide ions it must have. So: an acidic solution that has a large amount of H<sup>+</sup> will have very little OH<sup>–</sup>. And a basic solution that has very little H<sup>+</sup> will have more OH<sup>–</sup>. A solution that is exactly neutral will have the same amount of H<sup>+</sup> and OH<sup>–</sup>.

			==Calculating pH==
			To calculate pH, you should know the concentration of hydrogen ions (H<sup>+</sup>) in your solution. From there, the pH can be found by:

			<center><math> pH = -log_{10}([H^{+}]) </math></center>

			Since this is a logarithmic calculation, in order to change the pH by one unit (say, from 2 to 3), the concentration of H<sup>+</sup> must be changed by 10 times (say, from 0.01 mol/L to 0.001 mol/L).

			==Discover More==
			To explore pH further please see the [https://chem.libretexts.org/Core/Physical_and_Theoretical_Chemistry/Acids_and_Bases/Acids_and_Bases_in_Aqueous_Solutions/The_pH_Scale Chemistry LibreTexts page]. Also, the PhET simulation below was graciously provided by the University of Colorado. This simulation can help explore how pH changes as [[liquid]]s mix.

	<html>		<html>

J.williams: 1 revision imported

2015-08-26T21:31:43Z

1 revision imported

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J.williams at 17:00, 12 August 2015

2015-08-12T17:00:12Z

New page

[[Category:Done 2015-07-24]]
[[File:ph.jpg|300px|thumb|Figure 1. Various substances arranged by their pH.<ref>Wikimedia Commons [Online], Available: https://upload.wikimedia.org/wikipedia/commons/2/23/216_pH_Scale-01.jpg</ref>]]

<onlyinclude>The term '''pH''' is an abbreviation for '''power of Hydrogen''', which is a measure of the acidity or alkalinity (how base something is) of a [[chemical]] solution. Just like hot and cold are variations of [[temperature]], acidic and basic describe variations of chemical composition.</onlyinclude> Mixing an [[acid]] and [[base (chemistry)|base]] will balance out the acidity, just like mixing hot and cold water will balance out the temperature; a substance that is neither an acid nor a base is called "neutral".<Ref name=epa>US EPA. (July 8, 2015). ''What is pH?'' [Online], Available: http://www.epa.gov/acidrain/measure/ph.html</ref>

Acids and bases are very important in the world, and can be found almost everywhere. One main example in the context of energy is [[acid rain]], which is formed when water interacts with various [[pollutant]]s in the [[atmosphere]]. Acid rain is a concern of [[pollution]] and has many adverse effects on ecosystems and the [[environment]]. Read more about acid rain [[acid rain|here]].

==The pH scale==

The pH scale measures the concentration of [[hydrogen]] [[ion]]s (H+) within a substance; the larger the H+ concentration (number of molecules in a given volume), the lower the pH. Conversely, the larger the concentration of hydroxide ions (OH-), the higher the pH.<ref name=tool>Engineering Toolbox. (July 8, 2015). ''pH Definition'' [Online], Available: http://www.engineeringtoolbox.com/ph-d_483.html</ref> The pH scale ranges from 0 to 14 (extreme values are -1 and 15, but these are rarely encountered), with acids being defined as having a pH less than 7, and bases being defined as having a pH greater than 7. This makes 7 neutral, which is the pH of pure [[water]]. The reason pure water is neutral is because the concentration of H+ and OH- is exactly the same, therefore cancelling out.

The scale (Figure 1) is defined on a base 10 logarithmic scale, meaning that any 1 digit difference is 10 times more acidic or basic. For example, a pH of 1.0 is 10 times more acidic than a pH of 2.0, and it is 100 times more acidic than a pH of 3.0!

To explore pH further please see the [http://chemwiki.ucdavis.edu/Physical_Chemistry/Acids_and_Bases/Aqueous_Solutions/The_pH_Scale UC Davis chem wiki]. Also, the PhET simulation below was graciously provided by the University of Colorado. This simulation can help explore how pH changes as [[liquid]]s mix.

<html>
<iframe src="http://phet.colorado.edu/sims/html/ph-scale/latest/ph-scale_en.html" width="800" height="600"></iframe>
</html>

==References==
{{reflist}}
[[Category:Uploaded]]