Question

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

Answer 1

21. change in temperature, change in color, or noticeable odor (after reaction has begun)

22. Picture... Wasn't so sure about this since no charge was given, so I suspected it has a charge of 2. If you have more information on this I would be glad to help, and I can't tell what is happening with the calculations given. It would be helpful if you can add spaces or put a line break.

23. An ion is an atom or molecule with an electric charge. It is formed when atoms lose or gain electrons. There are two types of ions: cations (net positive charge) and anion (net negative charge).

24. Picture

25. a) dinitrogen tetrahydride

b) phosphorus triiodide

c) lithium hydroxide

Answer 2

See explanation.

Step-by-step explanation:

Hello,

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:

`n_(Zn(OH)_2)=0.45gZn(OH)_2*(1molZn(OH)_2)/(99.424gZn(OH)_2)=4.5x10^(-3)molZn(OH)_2`

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.
`Br^(-1)` as it has seven valance electrons, it needs one electron to attain the octet.

b.
`H^(+1)` as it loses one electron when forming a cation.

c.
`Se^(-2)` 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.

Best regards.