When I made my red cabbage indicator, I thought that the pH for bicarbonate of soda was too high so I decided to see if it was because I had made the bicarbonate to strong.
1 Mole is an amount of chemical that was invented about 200 years ago when atoms were too small to weigh. They reasoned that if you put a large number of atoms together, it would be heavy enough to weigh. Now it turns out that if you get the formula for the chemical and add up all the mass numbers (top numbers on the Periodic Table), then that mass in grams is worth 1 Mole. Next, if you dissolve that in 1000 cubic centimetres of water, the concentration comes out to be 1 Molar. I calculated that 0.84 grams in 100 cubic centimetres (same as millilitres) would be 0.1M.
So I zeroed the scales with the measuring jug on. I noticed that the RESOLUTION of these scales is + or - 1 gram - it measures to the nearest gram so I decided 1g would be close to 0.84g. I kept adding more and more powder and it still said zero.
Turns out that it won't measure anything less than 10 grams, so that's what I did. I tried to dissolve it in 100 cubic cm of water, but it wouldn't all dissolve so I went for 200 cubic cm. That works out as a concentration of 0.25M. I made 0.125M by doubling the amount of water to 400 cubic cm and stirring well.
I made 0.0625M by doubling the amount of water to 800 cubic cm. Concentration is INVERSELY PROPORTIONAL to volume of water: double the volume of water, halve the concentration.
Then I ran out of measuring jug so I poured half into another jug and doubled both to get 0.0313M.
Look! It doesn't matter how dilute you make it, the pH stays the same.
The reason is that pH depends on how much the molecule can dissociate into H+ and OH- ions. The more dissociation, the stronger the acid or alklai. The less dissociation, the closer to neutral. That is a property of the chemical and is not affected by diluting it.
