The acidity of a solution is typically assessed experimentally by measurement of its pH. The pOH of a solution is not usually measured, as it is easily calculated from an experimentally determined pH value. The pH of a solution can be directly measured using a pH meter (
[link] ).
(a) A research-grade pH meter used in a laboratory can have a resolution of 0.001 pH units, an accuracy of ± 0.002 pH units, and may cost in excess of $1000. (b) A portable pH meter has lower resolution (0.01 pH units), lower accuracy (± 0.2 pH units), and a far lower price tag. (credit b: modification of work by Jacopo Werther)
The pH of a solution may also be visually estimated using colored indicators (
[link] ).
(a) A universal indicator assumes a different color in solutions of different pH values. Thus, it can be added to a solution to determine the pH of the solution. The eight vials each contain a universal indicator and 0.1-
M solutions of progressively weaker acids: HCl (pH = l), CH
3 CO
2 H (pH = 3), and NH
4 Cl (pH = 5), deionized water, a neutral substance (pH = 7); and 0.1-
M solutions of the progressively stronger bases: KCl (pH = 7), aniline, C
6 H
5 NH
2 (pH = 9), NH
3 (pH = 11), and NaOH (pH = 13). (b) pH paper contains a mixture of indicators that give different colors in solutions of differing pH values. (credit: modification of work by Sahar Atwa)
Key concepts and summary
The concentration of hydronium ion in a solution of an acid in water is greater than 1.0
10
−7M at 25 °C. The concentration of hydroxide ion in a solution of a base in water is greater than 1.0
10
−7M at 25 °C. The concentration of
in a solution can be expressed as the pH of the solution; pH = −log
The concentration of OH
− can be expressed as the pOH of the solution: pOH = −log[OH
− ]. In pure water, pH = 7.00 and pOH = 7.00
Key equations
pOH = −log[OH
− ]
[H
3 O
+ ] = 10
−pH
[OH
− ] = 10
−pOH
pH + pOH = p
Kw = 14.00 at 25 °C
Chemistry end of chapter exercises
Explain why a sample of pure water at 40 °C is neutral even though [H
3 O
+ ] = 1.7
10
−7M .
Kw is 2.9
10
−14 at 40 °C.
In a neutral solution [H
3 O
+ ] = [OH
− ]. At 40 °C,
[H
3 O
+ ] = [OH
− ] = (2.910
−14 )
1/2 = 1.7
10
−7 .
The hydronium ion concentration in a sample of rainwater is found to be 1.7
10
−6M at 25 °C. What is the concentration of hydroxide ions in the rainwater?
Bacteria doesn't produce energy they are dependent upon their substrate in case of lack of nutrients they are able to make spores which helps them to sustain in harsh environments
_Adnan
But not all bacteria make spores, l mean Eukaryotic cells have Mitochondria which acts as powerhouse for them, since bacteria don't have it, what is the substitution for it?
Assimilatory nitrate reduction is a process that occurs in some microorganisms, such as bacteria and archaea, in which nitrate (NO3-) is reduced to nitrite (NO2-), and then further reduced to ammonia (NH3).
Elkana
This process is called assimilatory nitrate reduction because the nitrogen that is produced is incorporated in the cells of microorganisms where it can be used in the synthesis of amino acids and other nitrogen products
There are nothing like emergency disease but there are some common medical emergency which can occur simultaneously like Bleeding,heart attack,Breathing difficulties,severe pain heart stock.Hope you will get my point .Have a nice day ❣️
_Adnan
define infection ,prevention and control
Innocent
I think infection prevention and control is the avoidance of all things we do that gives out break of infections and promotion of health practices that promote life
