Answer:
Hydrogen ions
Explanation: pH is the concentration of hydrogen ions (H+) in a given solution. A pH of 1 means there are a lot of hydrogen ions and a pH of 14 means there is a very small concentration if them.
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A .present in many biological reactions
Explanation:
- A catalyst is a chemical substance that speeds up the rate of chemical reaction.
- It does not take part in the chemical reaction but facilitates the reaction.
- A homogenous catalyst is a catalyst that is present in the same phase as the reactants.
- The exact opposite is a heterogenous catalyst which is in a different phase from the reactants.
- Homogenous catalysts are present in many biological reactions.
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Answer:
number 4
Scientists may modify the idea as they gather more evidence.