What is the correct formula for Lead(IV) oxide? a. Pb2O4 b. Pb4O2 c. PbO d. PbO2 e. Pb2O 18. C2H2F4 is the formula for two possible molecules. C2H2F4 is an example of an a. structural formula b. empirical formula c. condensed formula d. space filling model. e. molecular formula 19. What is the name of the compound with the formula Cr2S3? a. chromium sulfide b chromium (II) sulfide c. chromium (III) sulfide d. chromium sulfate e. dichromium trisulfide 20. What is the correct formula for iron (III) sulfide? a. FeS3 b. Fe2S c. FeS d. Fe3S2 e. Fe2S3
The Correct Answer and Explanation is :
Here are the correct answers and explanations for each question:
17. What is the correct formula for Lead(IV) oxide?
Answer: d. PbO2
Explanation: Lead(IV) oxide has the chemical formula PbO2. In this case, the “IV” refers to the +4 oxidation state of lead (Pb), which requires it to bond with two oxygen atoms to balance the charge. Lead in the +4 oxidation state forms a stable oxide compound with oxygen, and the formula reflects that lead has a charge of +4, and each oxygen atom has a charge of -2. Hence, Pb (4+) and two O (2-) ions combine to form PbO2.
18. C2H2F4 is the formula for two possible molecules. C2H2F4 is an example of an:
Answer: e. molecular formula
Explanation: A molecular formula provides the actual number and type of atoms in a molecule, but not necessarily how they are arranged. C2H2F4 is the molecular formula because it indicates there are two carbon (C) atoms, two hydrogen (H) atoms, and four fluorine (F) atoms. While the compound might have different structural isomers, the molecular formula simply provides the count of atoms.
19. What is the name of the compound with the formula Cr2S3?
Answer: c. chromium (III) sulfide
Explanation: Chromium (III) sulfide is a compound where chromium has a +3 oxidation state and sulfur has a -2 oxidation state. The formula Cr2S3 indicates that two chromium atoms bond with three sulfur atoms. The “(III)” specifies the +3 oxidation state of chromium, and sulfur (being a Group 16 element) commonly has a -2 oxidation state. Thus, the correct name is chromium (III) sulfide.
20. What is the correct formula for iron (III) sulfide?
Answer: e. Fe2S3
Explanation: Iron (III) sulfide is a compound where iron has a +3 oxidation state and sulfur has a -2 oxidation state. To balance the charges, two iron ions (each with a +3 charge) combine with three sulfide ions (each with a -2 charge), resulting in the formula Fe2S3. The “(III)” in iron (III) indicates the +3 charge on the iron ions, which must be balanced by three sulfide ions.
These questions involve understanding oxidation states, molecular and empirical formulas, and the naming conventions for ionic compounds based on the charges of their ions.