Q: If you have 1 mole of O$$_2$$ gas, 1 mole of H$$_2O$$, and 1 mole of NaCl, which sample contains the greatest number of molecules?

All samples contain the same number of molecules: $$6.022 \times 10$$^{23}$$.

Q: Which of the following is the correct sequence for converting grams of CO$$_2 to $$number of CO$$_2$$ molecules?

$$\text{grams CO}_2 \rightarrow \text{moles CO}_2 \rightarrow \text{molecules CO}_2$$

Q: Which of the following statements about the mole is correct?

One mole of any substance contains $$6.022 \times 10$$^{23}$$ particles.

Question 1

Which of the following best explains why the properties of iron oxide (rust) are different from those of pure iron, as shown in the first image?

Accepted Answer

Iron oxide contains both iron and oxygen atoms chemically bonded, forming a new compound with different properties.

Question 2

Which type of chemical bond is most likely present in sodium chloride (NaCl)?

Accepted Answer

Ionic bond

Question 3

Given the molecular formula, structural formula, ball-and-stick model, and space-filling model of methane (CH$$_4) $$shown in the third image, which statement is correct?

Accepted Answer

All four representations show the same molecule but emphasize different aspects such as connectivity and spatial arrangement.

Question 4

Which of the following compounds is an example of a hydrocarbon used as a fuel, as shown in the fourth image?

Accepted Answer

Propane (C$$_3H$_8)$$

Question 5

A bottle of isopropyl rubbing alcohol is shown with its molecular model. Which functional group is present in isopropanol?

Accepted Answer

Alcohol group (–OH)

Question 6

Which of the following best describes the difference between ethene (C$$_2H$_4) $$and ethyne (C$$_2H$_2) as $$shown in the sixth image?

Accepted Answer

Ethene contains a double bond between carbon atoms, while ethyne contains a triple bond.

Question 7

If you have 1 mole of O$$_2$$ gas, 1 mole of H$$_2O$$, and 1 mole of NaCl, which sample contains the greatest number of molecules?

Accepted Answer

All samples contain the same number of molecules: $$6.022 	imes 10$$^{23}$$.

Question 8

How many moles of oxygen atoms are present in 1 mole of aspirin (C$$_9H$_8O$_4$$)?

Accepted Answer

$$4$$ moles

Question 9

Calculate the formula mass of water (H$$_2O) $$using the atomic masses: H = 1.01 amu, O = 16.00 amu.

Accepted Answer

$$18.02$$ amu

Question 10

A sample contains $$125.0 g of $$iron (III) chloride (FeCl$$_3). $$What is the number of moles in the sample? (Fe = 55.85 g/mol, Cl = 35.45 g/mol)

Accepted Answer

$$0.767$$ moles

Question 11

Which of the following 100.0-g samples contains the greatest number of oxygen atoms?

Accepted Answer

N$$_2O$$

Question 12

What is the empirical formula for a compound with the molecular formula C$$_6H$_{12}O$_6$$?

Accepted Answer

CH$$_2O$$

Question 13

A compound contains 47.08% carbon, 6.59% hydrogen, and 46.33% chlorine by mass. Its molar mass is 153 g/mol. What is its empirical formula?

Accepted Answer

C$$_2H$_4Cl$$

Question 14

Which of the following is the correct sequence for converting grams of CO$$_2 to $$number of CO$$_2$$ molecules?

Accepted Answer

$$	ext{grams CO}_2 ightarrow 	ext{moles CO}_2 ightarrow 	ext{molecules CO}_2$$

Question 15

A white powder contains 43.64% phosphorus and 56.36% oxygen by mass. Its molar mass is 283.88 g/mol. What is the empirical formula of the compound?

Accepted Answer

P$$_2O$_5$$

Question 16

Which of the following statements about the mole is correct?

Accepted Answer

One mole of any substance contains $$6.022 	imes 10$$^{23}$$ particles.

Question 17

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

Accepted Answer

The empirical formula shows the simplest whole-number ratio of atoms, while the molecular formula shows the actual number of atoms in a molecule.

Question 18

Calculate the mass percent of hydrogen in water (H$$_2O). (H = 1.01 g/$$mol, O = 16.00 g/mol)

Accepted Answer

$$11.2\%$$

Question 19

A sample of water has a mass of 59.8 grams. How many moles of water are in the sample? (Molar mass of H$$_2O = 18.02 g/$$mol)

Accepted Answer

$$3.32$$ moles

Chapter 3: Molecules and Compounds – Comprehensive Study Notes

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