21. list 3 indicators of a chemical change. a. b. c. 22. check the following problem for errors. if you find an error, identify it, tell why it is an error and correct the error solving the problem correctly. convert 0.45 g zinc hydroxide to moles. (hint: there are errors) 0.65 g znoh 82.41 mol = 3.22 x 10 25 mol 6.02x1023 g 23. what is an ion? explain how ions form. distinguish between a cation and an anion. be sure to use at least 3 to 4 complete content related sentences in your explanation. 24. write the symbol for the ion formed when each element gains electrons and attains a noble-gas electron configuration. a. br b. h c. se 25. name each of the compounds. there are ionic, covalent and acid/base compounds in the list. a. n2h4 b. pi3 c. lioh

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Explanation:

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21. In this case the three main indicators of a chemical change is a temperature change, a color change and/or the release of bubbles. All of them are indicators of a change in the composition of the initial reactants.

22. In this case, the correct conversion is:

In such a way three errors are: it starts by 0.45 g not 0.65 g, zinc hydroxide's molar mass is 99.424 g/mol as its formula is Zn(OH)₂ not 82.41 g/mol and the given Avogadro's number turns needless.

23. An ion is defined as a charged species coming from the ionization of an atom or a molecule, it means, when they either lose or gain electrons depending on the case. There exist two types of ions: cations (net positive charge) and anion (net negative charge).

24.

a. as it has seven valance electrons, it needs one electron to attain the octet.

b. as it loses one electron when forming a cation.

c. as it has six valance electrons, it needs two electrons to attain the octet.

25.

a. Hydrazine: covalent, base.

b. Phosphorus triiodide: covalent, base.

c. Lithium hydroxide: ionic, base.

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d.) gravity pulled particles of dust and gas together to form planets.