Compound Interest Acids, Alkalis, and the p. H Scale. Click to enlarge. The p. H scale is something were all familiar with most people will remember it from school chemistry lessons. Its the scale used to rank how strong an acid or alkali a solution is. The colours associated with each number correspond to the colour that universal indicator turns in solutions of that particular p. H. A fair proportion of people probably dont know the chemistry behind the p. H scale, though where exactly do these numbers come fromThe clues are actually partly hidden in the scales name. The H in p. H stands for the element, hydrogen. On a simple level, the p. H scale can be thought of as a ranking of the amount of hydrogen ions in a solution the more hydrogen ions, the lower the p. H number. The p in p. H, to chemists at least, stands for the mathematical operation log. H, then, is simply equal to log. The university holds an academic site license for ChemDraw Prime. This covers all university computers, and allows staff and students to download a copy for use on. The Chemistry Addin for Word allows students, chemists, and researchers to handle rich chemical structures within Microsoft Word. A selective, annotated collection of the best Web links for Chemistry educators. Comparative evaluation of chemical drawing programs Accelrys Symyx Draw, ChemDraw, DrawIt, ChemSketch, ChemDoodle, Chemistry 4D Draw, MarvinSketch, etc. A review. H, where H is the hydrogen ion concentration in a particular solution. Note that, strictly speaking, wed usually use H3. O to represent hydrogen ions, as this is the form they take in solutions. However, to keep things simple, well continue to use H here. Looking at the graphic above, you can see that an increase in p. Tiger Woods Pga Tour 11 Pc. H of one point actually involves a tenfold decrease in the concentration of hydrogen ions in a solution. The scale is whats known as a logarithmic scale. ProductManager/ChemDraw_for_iPad_03.jpg' alt='Chemdraw Full Version' title='Chemdraw Full Version' />Why do we bother with this mathematical manipulation in the first place Well, its clearly a lot easier to state a single number when referring to the acidity or alkalinity of a solution than it is to quote the many numbered hydrogen ion concentration. A p. H of spot on 7 denotes a neutral solution neither acidic or alkaline. Any p. H below 7 is acidic, whilst any p. H above 7 is termed alkaline. Water molecules have the chemical formula H2. O. However, these molecules are capable of splitting up slightly in solution, in H and OH hydroxide ions. In a neutral solution, the concentrations of these two ions are equal. However, the addition of an acid or alkali can cause them to vary. Acids are a source of hydrogen ions, and adding them to water increases the concentration of hydrogen ions in solution, lowering the concentration of hydroxide ions. For alkalis, the opposite is true they decrease the concentration of hydrogen ions, whilst increasing the concentration of hydroxide ions. Something a lot of people dont realise is that p. H is temperature dependent. Strictly speaking, pure water only has a p. H of 7 at room temperature 2. C.  Above and below this temperature, it can vary for example, at 1. C, the p. H of pure water is 6. Software for the modern chemical laboratory including freezer software, chemical inventory, molecular modeling and drawing. V16VkskGzTI/AAAAAAAAABs/XhzlPv6Ts5on2GHR0_xWGH5Fmx3mpzPMQCLcB/s1600/ChemOffice_Professional_fig1_ss.jpg' alt='Chemdraw Full Version' title='Chemdraw Full Version' />C, its 7. This doesnt mean that the pure water is becoming acidic or alkaline, but that, at these temperatures, those particular p. H numbers represent the neutral point. As a side note, its also worth pointing out that the p. H scale isnt limited to the usual 0 1. H values or values higher than 1. Another common misconception about p. H concerns the human body. Diets such as the alkaline diet claim that it is possible to affect the p. H value of your body by altering your diet to include alkalising foodstuffs that make the p. H of your body more alkaline. Whilst whats actually suggested, a diet heavy in fruits and vegetables, is certainly by no means unhealthy, its pretty much impossible for what you eat to change the p. H of your body. Im not going to go into too much detail, as Kat from The Chronicle Flask blog has already done an excellent job of debunking alkaline diets, but its worth reiterating a few key points. The p. H of the stomach can vary, between 1. H scale. However, this has no effect on the p. H of our body, or, more specifically, our blood. Human blood has a p. H value thats always slightly alkaline, between 7. If we were able to purposefully change the p. H of blood outside of this small range, we could actually cause ourselves a good deal of harm even a p. H change of 0. 5 either way could result in irreversible cell damage. Luckily, the food we eat has next to no effect on blood p. H. What we eat can affect the p. H of our urine. The p. H of urine has an average value of around 6, but can range between 4. However, whilst you might be able to have the slightest effect on your urinary p. H with your diet, its unrelated to the p. H of your blood this stays in the range previously stated, regardless of any change in urinary p. H. Moving on, and whilst were talking about acids, its worth talking about the strength of acids. Strictly speaking, its hard to place particular chemical compounds at specific points on the p. H scale, as their positions vary depending on concentration. Concentration is a measure of how much of a substance is dissolved in a solution. If we have a lot of an acid dissolved in a relatively small amount of water, wed say we have a solution with a high concentration. Similarly, if we had very little acid dissolved in lot of water, wed have a solution with a low concentration. Since concentration of solutions can easily be varied, solutions of varied concentration of the same acid can have different p. H values. Some acids, however, are stronger than others. Hydrochloric acid, the same acid found in stomach acid, is a strong acid as it can easily split up into its component ions. On the other hand, acetic acid, the acid found in vinegar, is a comparatively weak acid it doesnt split up into its component ions easily. Another example of a weak acid is hydrofluoric acid contrary to what a certain popular chemistry themed TV show would have you believe, its actually a fairly weak acid, which certainly couldnt dissolve a body. Its an unpleasant compound for different reasons though. We can rank acids in terms of their strength or how easily they split up into their component ions, but thats a topic for another post Enjoyed this post graphic Consider supporting Compound Interest on Patreon, and get previews of upcoming posts moreThe graphic in this article is licensed under a  Creative Commons Attribution Non. Commercial No. Derivatives 4. International License. See the sites content usage guidelines. References Further Reading. Global Collaboration and Analytics Platforms for Chemistry, Biology, and Clinical Research.