Randy Holmes-Farley
Reef Chemist
Staff member
Super Moderator
Excellence Award
Expert Contributor
Article Contributor
R2R Research
My Tank Thread
- Joined
- Sep 5, 2014
- Messages
- 67,349
- Reaction score
- 63,691
Reef Chemistry Question of the Day #204
Which of the following is the way that an ordinary alkalinity test kit works?
1. There is a dye in the test that binds to bicarbonate and which gives a different color when bound in that way. You add acid, which converts the bicarbonate into CO2, which doesn't bind to the dye, and hence the color changes when all the bicarbonate is used up this way.
2. There is a dye in the test that binds to carbonate and which gives a different color when bound in that way. You add acid, which converts the carbonate into CO2, which doesn't bind to the dye, and hence the color changes when all the carbonate is used up this way.
3. There is a dye in the test that can bind to a proton (H+) when enough protons are present in solution, and which gives a different color when bound in that way. You add acid (H+), which converts the dye to a different color. When you have added enough H+ to bind to a sufficient number of the dye molecules, the color changes and you are done.
4. There is a dye in the test that can bind to hydroxide ions (OH-) when enough hydroxide ions are present in solution, and which gives a different color when bound in that way. You add acid (H+), which reduces the amount of OH- in the water, removing OH- from the dye, and which converts the dye to a different color. When you have added enough H+ to unbind a sufficient number of the dye molecules from OH-, the color changes and you are done.
Good luck!
.
Which of the following is the way that an ordinary alkalinity test kit works?
1. There is a dye in the test that binds to bicarbonate and which gives a different color when bound in that way. You add acid, which converts the bicarbonate into CO2, which doesn't bind to the dye, and hence the color changes when all the bicarbonate is used up this way.
2. There is a dye in the test that binds to carbonate and which gives a different color when bound in that way. You add acid, which converts the carbonate into CO2, which doesn't bind to the dye, and hence the color changes when all the carbonate is used up this way.
3. There is a dye in the test that can bind to a proton (H+) when enough protons are present in solution, and which gives a different color when bound in that way. You add acid (H+), which converts the dye to a different color. When you have added enough H+ to bind to a sufficient number of the dye molecules, the color changes and you are done.
4. There is a dye in the test that can bind to hydroxide ions (OH-) when enough hydroxide ions are present in solution, and which gives a different color when bound in that way. You add acid (H+), which reduces the amount of OH- in the water, removing OH- from the dye, and which converts the dye to a different color. When you have added enough H+ to unbind a sufficient number of the dye molecules from OH-, the color changes and you are done.
Good luck!
.
