We have moved - but just up the street to 38 Chapel Street and our new hours are

Monday 0930 to 1730
Friday 0930 to 1730
Saturday 0930 to 1230

We are available for consultation and site visits at these times- other times by appointment by email (robin@soladome.com.au)

After 35 years at 44 Chapel Street it was time for a change to a web based operation and to offer guidance based on many years of practical experience.

 

 

pH - a more scientific definition

pH refers to the relative concentration of H+ ions in solution. The numerical value of the pH is the negative of the exponent of the molar concentration. Thus low pH values indicate high concentrations of H+ ions (acid), and high pH values indicate low concentrations...

pH refers to the relative concentration of H+ ions in solution. The numerical value of the pH is the negative of the exponent of the molar concentration. Thus low pH values indicate high concentrations of H+ ions (acid), and high pH values indicate low concentrations.

Ionisation - the process of spontaneous ion formation

H2O > OH- + H+

In 1 litre of water about 1 water molecule out of each 550 million is ionised at any instant in time corresponding to 1/10,000,000 of a mole of H+ ions ( a mole is defined as the weight in grams that corresponds to to the summed atomic weights of all the atoms of a molecule - its molecular mass. In the case of H+ the molecular mass equals 1, and a mole of H+ ions would weigh 1 gram.) The molar concentration of hydrogen ions in pure water, 1/10,000,000 can be written more easily by employing exponential notation. - count the number of decimal places after the digit "1" in the denominator

[H+] = 1/10,000,000

Brackets are used to indicate the chemical concentration of H+ . since there are 7 decimal places the molar concentration is 10 -7 moles per litre.

Any substance that dissociates to form H+ ions when dissolved in water is called an acid. The exponents in the exponential notation of H+ ion concentration are used as a convenient indication of acid strength called the pH scale. pH is normally expressed as a positive number and is the negative of the exponent of the molar concentration.

Pure water has a molar H+ concentration of 10 -7 and so a pH value of 7. The stronger the acid the more H+ ions it produces and so the lower its pH.

H+ ion
concentration
(moles/litre)

value

examples

OH- ion pH
concentration
(moles/litre)

10

-1

nitric acid

10-15

1

0

hydrochloric acid

10-14

10-1

1

stomach acid

10-13

10-2

2

lemon juice

10-12

10-3

3

vinegar,coca-cola

10-11

10-4

4

tomatoes

10-10

10-5

5

black coffee, normal rainwater

10-9

10-6

6

urine

10-8

10-7

7

pure water blood 10-7 tears

10-7

10-8

8

seawater

10-6

10-9

9

baking soda

10-5

10-10

10

great salt lake

10-4

10-11

11

household ammonia

10-3

10-12

12

bicarbonate of soda

10-2

10-13

13

oven cleaner

10-1

10-14

14

sodium hydroxide

1

10-15

15

drain opener

10