Chemistry Quiz: Atoms, Molecules, and Ions

What fundamental law does the experiment of decomposing hydrogen sulfide into hydrogen and sulfur demonstrate?

• Law of Conservation of Energy

• Law of Definite Proportions

• Law of Conservation of Mass

• Law of Multiple Proportions

Answer explanation

The experiment of decomposing hydrogen sulfide (H2S) into hydrogen (H2) and sulfur (S) demonstrates the fundamental law of conservation of mass, also known as Lavoisier's Law.

Explanation: According to the law of conservation of mass, mass is neither created nor destroyed in chemical reactions. In the experiment of decomposing hydrogen sulfide into hydrogen and sulfur, the total mass of the reactants (hydrogen sulfide) must be equal to the total mass of the products (hydrogen and sulfur). This means that the mass of hydrogen and sulfur produced must equal the mass of hydrogen sulfide decomposed. The experiment confirms this law by showing that the total mass remains constant before and after the chemical reaction, illustrating the conservation of mass.

Which of the following compounds is molecular in nature?

• CsBr

• Ag2SO4

• Sc2O3

• LiNO3

Answer explanation

• Molecular compounds consist of molecules formed by covalent bonds between nonmetal atoms.

• In "LiNO3," lithium (Li) is a metal, while nitrogen (N) and oxygen (O) are nonmetals.

• The presence of nitrogen and oxygen suggests that covalent bonds are formed between these nonmetal atoms, indicating a molecular nature.

• The other compounds listed, CsBr, Ag2SO4, and Sc2O3, contain metals combined with nonmetals. CsBr and Ag2SO4 are ionic compounds because they consist of a metal (Cs or Ag) bonded to a nonmetal (Br or SO4), and Sc2O3 is an ionic compound as well

What is the relative charge (in multiples of the electronic charge) of an electron?

• +1

• 0

• +2

• -1

Answer explanation

The relative charge of an electron is -1, which means it has a negative charge.

Which two of the following are isotopes of the same element: X1631, X1531, X1632?

• None of them

• X1631 and X1632

• X1531 and X1632

• X1631 and X1531

Answer explanation

Isotopes are atoms of the same element that have different numbers of neutrons in their nuclei. Based on the given symbols:

• X1631 and X1531 are isotopes of the same element because they have the same atomic number (number of protons), but different mass numbers (different numbers of neutrons).

• X1632 is not an isotope of the same element as X1631 and X1531 because it has a different atomic number (since it has a different number of protons).

So, X1631 and X1531 are isotopes of the same element.

What do ethane and ethanol have in common?

• Same molecular formula

• Same functional group

• Same empirical formula

• Same number of carbon atoms

Answer explanation

Ethane and ethanol are both organic compounds that share some similarities:

1. Both contain carbon (C), hydrogen (H), and oxygen (O) atoms.

2. They are both composed of carbon chains: ethane has a two-carbon chain (C2H6), and ethanol has a two-carbon chain with an attached hydroxyl (-OH) group (C2H5OH).

3. They are both used as fuels: ethane is primarily used as a feedstock in the production of ethylene, a precursor to plastics, while ethanol is commonly used as a biofuel and as an alcohol in beverages and industrial processes.

4. They are both flammable.

5. Both ethane and ethanol are nonpolar molecules. Ethane has only carbon-hydrogen bonds, which are nonpolar, while ethanol has a polar -OH group but is mostly nonpolar due to the predominance of the hydrocarbon chain.

Locate the element Sc in the periodic table. Is it a metal, metalloid, or nonmetal?

• Nonmetal

• Noble Gas

• Metal

• Metalloid

Answer explanation

Scandium (Sc) is located in the fourth period (row) and the third group (column) of the periodic table. It is classified as a metal.

Which of the following compounds is ionic in nature?

• NF3

• NOCl

• B2H6

• Ba(OH)2

Answer explanation

• Ionic compounds typically consist of a metal combined with a nonmetal or a polyatomic ion.

• In "Ba(OH)2", Ba (barium) is a metal, while OH (hydroxide) is a polyatomic ion composed of a nonmetal (oxygen) and a hydrogen.

• The presence of a metal (Ba) combined with a polyatomic ion (OH) suggests an ionic bond.

• The other compounds listed, NF3, NOCl, and B2H6, consist of nonmetals only or nonmetals bonded with other nonmetals, indicating covalent bonding rather than ionic bonding.

What is a hydrocarbon?

• A compound containing only hydrogen

• A compound containing only carbon

• A compound containing only noble gases

• A compound containing carbon and hydrogen

Give the chemical formula for the chlorate ion.

• ClO3-

• ClO4-

• Cl-

• ClO2-

What is the molecular formula of pentane?

• C5H12

• C4H10

• C6H14

• C3H8