Question 1

Which of the following best explains why the formula for magnesium phosphate is $$\mathrm{Mg_3$(PO_4$)_2}$$?

Accepted Answer

Because three magnesium ions are needed to balance the charge of two phosphate ions, resulting in a neutral compound.

Question 2

Given the charges on $$\mathrm{Mg$$^{2+}$$}$$ and $$\mathrm{PO_4$^{3-}}$$, what is the total positive charge contributed by magnesium ions in $$\mathrm{Mg_3$(PO_4$)_2}$$?

Accepted Answer

$$+6$$

Question 3

In the compound $$\mathrm{Mg_3$(PO_4$)_2}$$, what is the total negative charge contributed by the phosphate ions?

Accepted Answer

$$-6$$

Question 4

Why is it necessary to use parentheses around $$\mathrm{PO_4$} in $$the formula $$\mathrm{Mg_3$(PO_4$)_2}$$?

Accepted Answer

Because there are two phosphate ions and parentheses indicate that the subscript applies to the entire polyatomic ion.

Question 5

If the charge on the phosphate ion were $$-2$$ instead of $$-3$$, what would be the correct formula for magnesium phosphate?

Accepted Answer

Question 6

What is the correct way to write the formula for a compound formed between $$\mathrm{Al$$^{3+}$$}$$ and $$\mathrm{SO_4$^{2-}}$$?

Accepted Answer

$$\mathrm{Al_2$(SO_4$)_3}$$

Question 7

Which statement about the charges in $$\mathrm{Mg_3$(PO_4$)_2} is $$correct?

Accepted Answer

The total positive charge equals the total negative charge, making the compound neutral.

Question 8

If you were to write the formula for calcium phosphate, given $$\mathrm{Ca$$^{2+}$$}$$ and $$\mathrm{PO_4$^{3-}}$$, what would it be?

Accepted Answer

$$\mathrm{Ca_3$(PO_4$)_2}$$

Question 9

What is the charge on the magnesium ion in $$\mathrm{Mg_3$(PO_4$)_2}$$?

Accepted Answer

$$+2$$

Question 10

Which of the following best describes the relationship between the subscripts in $$\mathrm{Mg_3$(PO_4$)_2}$$ and the charges of the ions?

Accepted Answer

The subscript of each ion is equal to the charge of the other ion (ignoring sign) to balance the total charges.

Ionic Compounds: Structure, Formation, and Properties

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