Q: Which of the following is the correct balanced equation for the combustion of methane (CH$$_4$$)?

$$\text{CH}_4(g) + 2\text{O}_2(g) \rightarrow \text{CO}_2(g) + 2\text{H}_2\text{O}(g)$$

Q: How many oxygen atoms are present in 2 moles of H$$_2O$$?

$$2.41 \times 10$$^{24}$$ atoms

Question 1

Which of the following statements best explains why water (H$$_2O) $$has a higher boiling point than methane (CH$$_4$$)?

Accepted Answer

Water molecules form strong hydrogen bonds, while methane molecules only experience weak dispersion forces.

Question 2

A bond between sodium (Na, electronegativity = 0.9) and chlorine (Cl, electronegativity = 3.0) is best classified as:

Accepted Answer

Ionic, because the electronegativity difference is $$3.0 - 0.9 = 2.1$$

Question 3

Which of the following molecules is nonpolar?

Accepted Answer

CCl$$_4$$

Question 4

What is the main intermolecular force present in solid NaCl at room temperature?

Accepted Answer

Ionic bonds

Question 5

Which of the following is an indicator that a chemical reaction has occurred?

Accepted Answer

Formation of a solid precipitate

Question 6

Given the reaction: $$2 	ext{Fe}(s) + 3 	ext{S}(s) \rightarrow 	ext{Fe}_2	ext{S}_3(s)$$, how many moles of Fe are required to react completely with 6 moles of S?

Accepted Answer

$$4$$ moles

Question 7

Which of the following best describes a combustion reaction?

Accepted Answer

A hydrocarbon reacts with O$$_2 to $$produce CO$$_2$$, H$$_2O$$, and energy.

Question 8

What is the molar mass of H$$_2SO$_4 ($$sulfuric acid)? (H = 1.01 g/mol, S = 32.07 g/mol, O = 16.00 g/mol)

Accepted Answer

$$98.09 g/$$mol

Question 9

A sample contains $$3.01 	imes 10$$^{23}$$ molecules of CO_2$. How many moles of CO_2$ are present?

Accepted Answer

$$0.5$$ mol

Question 10

Which of the following best explains why NH$$_3 ($$ammonia) is a polar molecule?

Accepted Answer

The dipoles do not cancel due to the molecule's shape, resulting in a net dipole moment.

Question 11

If the electronegativity difference between two atoms is $$0.7$$, what type of bond is formed?

Accepted Answer

Polar covalent

Question 12

Which of the following is the correct balanced equation for the combustion of methane (CH$$_4$$)?

Accepted Answer

$$	ext{CH}_4(g) + 2	ext{O}_2(g) ightarrow 	ext{CO}_2(g) + 2	ext{H}_2	ext{O}(g)$$

Question 13

A student mixes 10.0 g of A (molar mass = 20.0 g/mol) with 10.0 g of B (molar mass = 10.0 g/mol) in the reaction $$A + 2B \rightarrow AB_2$. Which is the limiting reactant?

Accepted Answer

A

Question 14

Which of the following best describes the law of conservation of mass in a chemical reaction?

Accepted Answer

The total mass of reactants equals the total mass of products.

Question 15

How many oxygen atoms are present in 2 moles of H$$_2O$$?

Accepted Answer

$$2.41 	imes 10$$^{24}$$ atoms

Question 16

Which of the following is a correct mole-to-mole ratio from the balanced equation $$2	ext{Fe}(s) + 3	ext{S}(s) \rightarrow 	ext{Fe}_2	ext{S}_3(s)$$?

Accepted Answer

$$2$$ moles Fe : $$3$$ moles S

Question 17

A reaction has a theoretical yield of 50.0 g, but only 40.0 g of product is actually obtained. What is the percent yield?

Accepted Answer

$$80\%$$

Question 18

Which of the following best describes a double replacement reaction?

Accepted Answer

The positive ions in two compounds switch places.

Question 19

Which of the following statements about dispersion forces is correct?

Accepted Answer

They are the only intermolecular forces present in nonpolar molecules.

CHE 100: Electronegativity, Bond Polarity, and Types of Chemical Bonds

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