Q: What is the formula mass of glucose ($\mathrm{C_6H_{12}O_6}$)? Use atomic masses: C = 12.01 amu, H = 1.008 amu, O = 16.00 amu.

$\mathrm{6 \times 12.01 + 12 \times 1.008 + 6 \times 16.00 = 180.16\ amu}$

Q: A tablet contains 200 mg of ibuprofen ($\mathrm{C_{13}H_{18}O_2}$). How many molecules are present? (Molar mass = 206.29 g/mol, Avogadro's number = $6.022 \times 10^{23}$)

$\mathrm{200 \times 10^{-3}\ g \div 206.29\ g/mol \times 6.022 \times 10^{23} = 5.84 \times 10^{20}}$

Q: What is the mass percent of oxygen in acetic acid ($\mathrm{C_2H_4O_2}$)? (Atomic masses: C = 12.01 g/mol, H = 1.008 g/mol, O = 16.00 g/mol)

$\mathrm{2 \times 16.00 \div (2 \times 12.01 + 4 \times 1.008 + 2 \times 16.00) \times 100\% = 40.00\%}$

Question 1

Which statement best explains why water (H2O) has properties dramatically different from hydrogen and oxygen gases?

Accepted Answer

Water is a compound formed by a fixed ratio of hydrogen and oxygen atoms, resulting in new properties.

Question 2

Which law states that a compound always contains the same proportion of elements by mass?

Accepted Answer

Law of Definite Proportion

Question 3

What is the empirical formula for a compound with the molecular formula C2H4O2?

Accepted Answer

CH2O

Question 4

Which type of chemical bond involves the transfer of electrons from a metal to a nonmetal?

Accepted Answer

Ionic bond

Question 5

What is the correct formula for the compound formed between magnesium and nitrogen?

Accepted Answer

Mg3N2

Question 6

Which statement about ionic solids is true according to Lewis theory?

Accepted Answer

Ionic solids are hard and brittle, and do not conduct electricity in the solid state.

Question 7

What is the name of the compound FeS?

Accepted Answer

Iron(II) sulfide

Question 8

Which polyatomic ion is present in NaNO2 and what is its charge?

Accepted Answer

Nitrite, $\mathrm{NO_2^-}$, charge -1

Question 9

What is the systematic name for MgSO4 \cdot 7H2O?

Accepted Answer

Magnesium sulfate heptahydrate

Question 10

Which element can form double and triple covalent bonds with itself?

Accepted Answer

Carbon

Question 11

What is the formula mass of glucose ($\mathrm{C_6H_{12}O_6}$)? Use atomic masses: C = 12.01 amu, H = 1.008 amu, O = 16.00 amu.

Accepted Answer

$\mathrm{6 	imes 12.01 + 12 	imes 1.008 + 6 	imes 16.00 = 180.16\ amu}$

Question 12

A tablet contains 200 mg of ibuprofen ($\mathrm{C_{13}H_{18}O_2}$). How many molecules are present? (Molar mass = 206.29 g/mol, Avogadro's number = $6.022 	imes 10^{23}$)

Accepted Answer

$\mathrm{200 	imes 10^{-3}\ g \div 206.29\ g/mol 	imes 6.022 	imes 10^{23} = 5.84 	imes 10^{20}}$

Question 13

What is the mass percent of oxygen in acetic acid ($\mathrm{C_2H_4O_2}$)? (Atomic masses: C = 12.01 g/mol, H = 1.008 g/mol, O = 16.00 g/mol)

Accepted Answer

$\mathrm{2 	imes 16.00 \div (2 	imes 12.01 + 4 	imes 1.008 + 2 	imes 16.00) 	imes 100\% = 40.00\%}$

Question 14

A compound has the empirical formula CH and a molar mass of 78.11 g/mol. What is its molecular formula?

Accepted Answer

$\mathrm{C_6H_6}$

Question 15

Upon combustion, a compound containing only carbon and hydrogen produces 1.60 g CO2 and 0.819 g H2O. What is the empirical formula?

Accepted Answer

$\mathrm{C_5H_{12}}$

Question 16

Which of the following is the correct name for PCl5?

Accepted Answer

Phosphorus pentachloride

Question 17

What is the correct formula for the compound formed between aluminum and nitrogen?

Accepted Answer

AlN

Question 18

Which statement about organic compounds is correct?

Accepted Answer

Organic compounds are mainly composed of carbon and hydrogen, sometimes with O, N, P, S.

Chapter 4: Molecules and Compounds – Structure, Bonding, and Composition

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