The hard parts of an organism, such as shells and bones.
Answer:

Explanation:
Hello,
In this case, for the acid dissociation of formic acid (HCOOH) we have:

Whose equilibrium expression is:
![Ka=\frac{[H^+][HCOO^-]}{[HCOOH]}](https://tex.z-dn.net/?f=Ka%3D%5Cfrac%7B%5BH%5E%2B%5D%5BHCOO%5E-%5D%7D%7B%5BHCOOH%5D%7D)
That in terms of the reaction extent is:

Thus, solving for
which is also equal to the concentration of hydrogen ions we obtain:

![[H^+]=0.00528M](https://tex.z-dn.net/?f=%5BH%5E%2B%5D%3D0.00528M)
Then, as the pH is computed as:
![pH=-log([H^+])](https://tex.z-dn.net/?f=pH%3D-log%28%5BH%5E%2B%5D%29)
The pH turns out:

Regards.
An investigator can collect hairs they observe visually (with tweezers or by hand), and they can also use clear tape to lift non-visible hair from a variety of surfaces, such as clothing. Other methods of hair sample collection include combing and clipping methods.
Answer:
The change in POP can not be reversed hence it is a chemical change.
Explanation:
Plaster of Paris (POP) is used to immobilize a fractured bone. The POP sets when water is added to it, it hardens irreversibly. Once it hardens, its shape can not be changed by any physical means. This means that the hardening of POP is a chemical change.
The chemical name of plaster of Paris is calcium sulfate hemihydrate. The setting of POP is an example of a chemical reaction.