Q: What is the formula mass of $$\mathrm{$$MgCl_2$$}$$? (Atomic masses: Mg = 24.3, Cl = 35.5)

$$24.3 + 2 \times 35.5 = 95.3$$

Question 1

Which of the following statements best explains why the properties of sodium chloride (NaCl) differ from those of its constituent elements, sodium and chlorine?

Accepted Answer

NaCl is a compound, and compounds generally have properties different from the elements that compose them.

Question 2

Which of the following best describes the law of constant composition?

Accepted Answer

All samples of a given compound have the same proportions of their constituent elements.

Question 3

A sample of water is decomposed into 16.0 grams of oxygen and 2.0 grams of hydrogen. What is the mass ratio of oxygen to hydrogen in water?

Accepted Answer

$$\frac{16.0}{2.0} = 8.0$$

Question 4

Which of the following is a correct chemical formula for a compound containing magnesium and chlorine?

Accepted Answer

MgCl$$_2$$

Question 5

What is the empirical formula for hydrogen peroxide, whose molecular formula is $$\mathrm{H_2O_2}$$?

Accepted Answer

$$\mathrm{HO}$$

Question 6

Which of the following elements exists naturally as a diatomic molecule?

Accepted Answer

Chlorine (Cl$$_2)$$

Question 7

Which of the following best distinguishes a compound from a mixture?

Accepted Answer

A compound has a fixed, definite proportion of elements; a mixture has variable proportions.

Question 8

Which of the following is the correct formula for the ionic compound formed from aluminum and oxygen?

Accepted Answer

Al$$_2O$_3$$

Question 9

How many oxygen atoms are present in one formula unit of $$\mathrm{Mg(NO_3$)_2}$$?

Accepted Answer

6

Question 10

Which of the following statements about chemical formulas is correct?

Accepted Answer

Changing a subscript in a chemical formula creates a different compound.

Question 11

Which of the following is a molecular compound?

Accepted Answer

CO$$_2$$

Question 12

What is the formula mass of $$\mathrm{$$MgCl_2$$}$$? (Atomic masses: Mg = 24.3, Cl = 35.5)

Accepted Answer

$$24.3 + 2 	imes 35.5 = 95.3$$

Question 13

Which of the following best describes an ionic compound?

Accepted Answer

A compound formed from a metal and a nonmetal, containing cations and anions.

Question 14

Which of the following is the correct formula for the compound formed from calcium and nitrate ions?

Accepted Answer

Ca(NO$$_3$$)$$_2$$

Question 15

Which of the following is the correct order for writing elements in a chemical formula?

Accepted Answer

The most metallic element is written first.

Question 16

Which of the following is NOT a diatomic element?

Accepted Answer

Sulfur (S$$_8)$$

Question 17

Which of the following best describes the difference between empirical and molecular formulas?

Accepted Answer

The empirical formula shows the simplest whole-number ratio; the molecular formula shows the actual number of atoms.

Question 18

How many nitrogen atoms are present in one formula unit of $$\mathrm{Mg(NO_3$)_2}$$?

Accepted Answer

2

Question 19

Which of the following is a correct statement about the composition of compounds?

Accepted Answer

Compounds have a constant composition with respect to mass and atom ratio.

Question 20

Which of the following is the correct formula for the ionic compound formed from magnesium and oxygen?

Accepted Answer

MgO

Chapter 5: Molecules and Compounds – Structured Study Notes

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