What is the pH scale and what is it?

Answer 1

The pH scale measures how acidic or basic a substance is. It ranges from 0 to 14. A pH of 7 is neutral. A pH less than 7 is acidic, and a pH greater than 7 is basic. Each whole pH value below 7 is ten times more acidic than the next higher value. For example, a pH of 4 is ten times more acidic than a pH of 5 and 100 times (10 times 10) more acidic than a pH of 6. The same holds true for pH values above 7, each of which is ten times more alkaline—another way to say basic—than the next lower whole value. For example, a pH of 10 is ten times more alkaline than a pH of 9.

Answer 2

A measure of how acidic a solution is. An acid is often defined as anything that increases the concentration of H+ ions in a solution. So a simple and obvious way to measure acidity is to measure the concentration of H+, but that can range over a wide scale. We commonly encounter substances with H+ concentrations ranging from 1 M (fairly concentrated strong acids) to 10^-14 M (fairly concentrated strong bases, which remove H+), with 10^-7 M being neutral. (Don't worry if you don't know what a M is--just accept that it's a unit of concentration.)

These numbers are a pain to work with, so the pH scale was invented. The way it works is, first you take the concentration of H+--say, 10^-7, a neutral solution. Then, you take the logarithm of it. The logarithm is the power that 10 would have to be raised to to equal that number. For a number like 10^-7, it's easy to see that the logarithm is -7. For numbers that aren't powers of ten, like, say, 5 * 10^-7, you have to use a calculator, although you could guess that it'll be between -7 and -6.

Anyway, after you take the logarithm, you multiply it by -1 to get the pH. So if your original solution had an H+ concentration of 10^-7, the pH is 7.

This system means that acidity can be defined on a small scale that's easy to think about. Remember, I said that we often encounter substances with H+ concentrations ranging rom 1 to 10^-14? With the pH scale, those same substances ranges from 0 to 14.

Answer 3

pH is defined as the negative log, base 10, of the concentration of hydrogen ions, also known as hydronium ions. By implication, it also specifies the concentration of OH- ions.

The dissociaiton constant for water is 10^-14. This means that the concentration of H+ ions times the concentration of OH- ions is 10^-14.

If the concentraion of ions is equal, each will be 10^-7. The log of 10^-7 is -7. The negative log is 7, so a neutral solution has a pH of 7.

If the pH is less than 7, the H+ ions are greater than th OH- ions and the solution is acidic. If the pH is above 7, the OH- ions outnumber the H+ ions and the solution is basic.

Answer 4

Refinements to other answers:

The pH scale does NOT range from 0 to 14. pH is defined as –log[H+], and it's possible to make solutions of [H+] or [OH–] greater than 1.0. For example, 12M HCl therefore has [H+] = 12M, which has a pH of –1.1. 12M NaOH has a pH of 15.1.

pH 7 does NOT guarantee a neutral solution, with [H+] = [OH–]. This is true only at 25ºC. pH 7 means [H+] = 1E–7 M, which happens to be the same as the [OH–] at 25º, but not at any other temperature. The dissociation constant for water is temperature dependent, just like any K value. At you increase T, the equilbirium shifts to > 1E–7 M for both ions, so that neutral will be pH (and pOH) <7.

Answer 5

I'm not quite sure but I know it is a scale of acidity and akaline(ity?) 1 being the most acidic and 14ish bing the most alkaine. This n the universal indicator scale where it goes red to purple (1 to 14) green and 8 are neutral. Some indicators like methyl orange ( used for strong acid and weak alkaline) changes from orange to purple when the substance beomes acidic but won't tell you the scale of the acid. I can't think of a solid acid or a liquid alkaline.

Answer 6

pH is a measure of the acidity of a solution in terms of activity of hydrogen (H+). For dilute solutions, however, it is convenient to substitute the activity of the hydrogen ions with the molarity (mol/L) of the hydrogen ions (however, this is not necessarily accurate at higher concentrations )
In aqueous systems, the hydrogen ion activity is dictated by the dissociation constant of water (Kw = 1.011 × 10−14 M2 at 25 °C) and interactions with other ions in solution. Due to this dissociation constant, a neutral solution (hydrogen ion activity equals hydroxide ion activity) has a pH of approximately 7. Aqueous solutions with pH values lower than 7 are considered acidic, while pH values higher than 7 are considered basic.
The concept was introduced by S.P.L. Sørensen in 1909, and is purported to mean pondus hydrogenii in Latin.However, most other sources attribute the name to the French term pouvoir hydrogène.In English, pH can stand for "hydrogen power,""power of hydrogen," All of these terms are technically correct.

pH can be measured:
by addition of a pH indicator into the studying solution. The indicator color varies depending on the pH of the solution. Using indicators, qualitative determinations can be made with universal indicators that have broad color variability over a wide pH range and quantitative determinations can be made using indicators that have strong color variability over a small pH range. Extremely precise measurements can be made over a wide pH range using indicators that have multiple equilibriums in conjunction with spectrophotometric methods to determine the relative abundance of each pH dependent component that make up the color of solution, or
by using a pH meter together with pH-selective electrodes (pH glass electrode, hydrogen electrode, quinhydrone electrode, ion sensitive field effect transistor and others).
As the pH scale is logarithmic; it doesn't start at zero. Thus the most acidic of liquids encountered can have a pH of as low as -5. The most alkaline typically has pH of 14.

An indicator is used to measure the pH of a substance. Common indicators are litmus paper, phenolphthalein, methyl orange, phenol red, bromothymol blue, and bromocresol purple. To demonstrate the principle with common household materials, red cabbage, which contains the dye anthocyanin, is used.

Answer 7

pH is a measure of the acidity of a solution in terms of activity of hydrogen (H+).

Answer 8

th ph scale is the measuremnt of acidity it tells how much acid is in a object

Answer 9

pH scale measure the acid and/alkaline content.

Answer 10

percent hydrogen, measurement of free hydrogen ions and therefore acid/base