Question 1

Which statement best explains why the chemical and physical properties of water ($\mathrm{H_2O}$) are different from those of its constituent elements, hydrogen ($\mathrm{H_2}$) and oxygen ($\mathrm{O_2}$)?

Accepted Answer

Water is a compound formed by a chemical reaction, resulting in new properties distinct from those of hydrogen and oxygen.

Question 2

Which of the following best describes the difference between ionic and covalent bonds?

Accepted Answer

Ionic bonds involve the transfer of electrons from one atom to another, while covalent bonds involve the sharing of electrons between atoms.

Question 3

Given the empirical formula $\mathrm{CH_2O}$ and a molar mass of $180\ \mathrm{g/mol}$, what is the molecular formula of the compound?

Accepted Answer

$\mathrm{C_6H_{12}O_6}$

Question 4

Which rule is used to predict how many electrons atoms tend to have in their valence shell when forming covalent compounds?

Accepted Answer

The octet rule

Question 5

Which of the following statements about ionic compounds is correct?

Accepted Answer

Ionic compounds conduct electricity when dissolved in water or melted.

Question 6

What is the correct formula for magnesium chloride, given that magnesium forms $\mathrm{Mg^{2+}}$ ions and chloride forms $\mathrm{Cl^-}$ ions?

Accepted Answer

$\mathrm{MgCl_2}$

Question 7

Which of the following best describes lattice energy in ionic compounds?

Accepted Answer

The energy released when gaseous ions combine to form an ionic solid.

Question 8

A compound contains 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. What is its empirical formula?

Accepted Answer

$\mathrm{CH_2O}$

Question 9

Which of the following is the correct Lewis structure for a water molecule ($\mathrm{H_2O}$)?

Accepted Answer

Oxygen atom with two single bonds to hydrogen atoms and two lone pairs of electrons.

Question 10

Which of the following compounds is a molecular compound?

Accepted Answer

$\mathrm{CO_2}$

Question 11

What is the molar mass of $\mathrm{C_2H_6O}$ (ethanol)?

Accepted Answer

$46\ \mathrm{g/mol}$

Question 12

A sample contains $0.50$ moles of $\mathrm{NaCl}$. How many grams of $\mathrm{NaCl}$ are present? ($\mathrm{NaCl}$ molar mass = $58.44\ \mathrm{g/mol}$)

Accepted Answer

$29.22\ \mathrm{g}$

Question 13

Which of the following is the correct name for $\mathrm{N_2O_5}$?

Accepted Answer

Dinitrogen pentoxide

Question 14

Which statement about valence electrons is true according to Lewis theory?

Accepted Answer

Valence electrons are involved in the sharing or transfer of electrons during bond formation.

Question 15

A compound has a molar mass of $84\ \mathrm{g/mol}$ and an empirical formula of $\mathrm{C_2H_4O}$. What is its molecular formula?

Accepted Answer

$\mathrm{C_4H_8O_2}$

Question 16

Which of the following is NOT a correct rule for naming ionic compounds?

Accepted Answer

Prefixes are used to indicate the number of atoms in ionic compounds.

Question 17

Which of the following best describes the composition of $\mathrm{CO_2}$ by mass? (Molar mass $= 44.01\ \mathrm{g/mol}$; C $= 12.01\ \mathrm{g/mol}$, O $= 16.00\ \mathrm{g/mol}$)

Accepted Answer

Carbon: $27.3\%$, Oxygen: $72.7\%$

Question 18

Which of the following is a correct molecular formula for a compound containing 2 nitrogen atoms and 4 oxygen atoms?

Accepted Answer

$\mathrm{N_2O_4}$

Question 19

Which of the following statements about hydrogen in covalent compounds is correct?

Accepted Answer

Hydrogen prefers to be surrounded by two valence electrons.

Question 20

A student determines the empirical formula of a compound to be $\mathrm{CH}$ and its molar mass to be $78\ \mathrm{g/mol}$. What is the molecular formula?

Accepted Answer

$\mathrm{C_6H_6}$

Chem chapter 4 study guide

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