CHEM 2: Standard Quiz 2
Name:________________________________________ Section #:_________________ Points: _____ / 25
Please read each question carefully. Show your work, and partial credit will be awarded where possible. Report all
answers with the correct number of significant figures.
Section 1: Empirical & Molecular Formulas
1.
(1 point) Circle ANY formula below which is a reasonable EMPIRICAL formula.
A. C2H4O2
B. C2H4O
C. C6H12O6
D. All of the above are reasonable empirical formulas.
E. None of the above are reasonable empirical formulas.
2.
(1 point) The molecular formula of tribromobenzene is C6H3Br3. What is the corresponding EMPIRICAL formula for
tribromobenzene?
A. In this case, the molecular formula equals the empirical formula: C6H3Br3
B. C4HBr
C. C3HBr
D. C2HBr
E. None of the above are the proper empirical formula for tribromobenzene.
3.
(1 point) The molecular formula of caffeine is C8H10N4O2. What is the corresponding EMPIRICAL formula for caffeine?
A. In this case, the molecular formula equals the empirical formula: C8H10N4O2
B. C4H5N2O2
C. C4H5N2O
D. C2H5N2O
E. None of the above are the proper empirical formula for caffeine.
4.
(3 points) A compound containing ONLY selenium and fluorine is found to contain 40.92 % selenium by mass. What is the
EMPIRICAL formula of this compound?
5.
(2 points) A molecule with a molar mass of 312.29 g/mol is found to have an empirical formula of C3H2N. What is the
MOLECULAR formula of this compound?
CHEM 2: Standard Quiz 2
Section 2: Chemical Reactions
Categorize each reaction below as A.) Synthesis, B.) Double Replacement, C.) Combustion, or D.) Decomposition. There
may be more than one of each category. (1 point each)
________ 6.
8 SF6 → S8 + 24 F2
________ 7.
8 Mg + S8 → 8 MgS
________ 8.
Ag3PO4 + 3 KBr → 3 AgBr + K3PO4
________ 9.
2 C2H2 + 5 O2 → 4 CO2 + 2 H2O
________10.
CaCO3 → CaO + CO2
11. (2 points) Circle any of the compounds below that would be insoluble in water.
A. Ba(NO3)2
B. BaBr2
C. AgF
D. Ag2SO4
E.
Cu2SO4
12. (3 points) Write the balanced equation for the reaction that occurs when aqueous barium nitrate is mixed with aqueous
sodium carbonate. Be sure to write the phases of all components in the reaction.
13. (2 points) Trinitramide, N(NO2)3, has a potential use as one of the most efficient and least polluting of rocket propellant
oxidizers. Write the balanced equation for the decomposition of N(NO2)3 to produce nitrogen gas and oxygen gas.
14. (3 points) Write the balanced equation for the complete combustion of C6H14.
15. (2 points) Write the balanced equation for the synthesis of Fe2S3 starting from iron metal and sulfur (as S8).
CHEM 2: Standard Quiz 2
Extra Credit: 3 points
Upon detonation, trinitrotoluene (TNT) decomposes into nitrogen gas, water vapor, carbon monoxide, and carbon atoms
(soot). Write the balanced chemical equation for this decomposition.
HINT: the formula of TNT is C7H5N3O6