Sample Questions for the Rhode Island High School Chemistry Contest
Instructors have frequently asked for sample questions or old exams to get the flavor of future exams. This page provides some sample questions. Clicking on the "Explanation" provides the correct answer and a brief explanation to the question.
1. How many significant figures are there in the measured number 0.0000730500?
2. The formula for hypochlorous acid is
3. "Amorphous" refers to
A. a lover's quarrel.
B. something that can act as an acid or a base.
C. one of three types of calcination that can be performed in a vacuum.
D. a material that is combined with mercury.
E. something lacking definite crystalline structure.
4. What is the pH of a 1.0×1010 M aqueous solution of hydrochloric acid?
5. All other things being equal, which of the following acids would be the best choice for making a buffer for pH = 4.26?
A. Formic acid, molar mass = 46.03
B. Butanoic acid, melting point = 4.26 °C
C. Acetoacetic acid, Ka = 2.62×104
D. Ethylphenylacetic acid, Ka = 4.27×105
E. m-Chlorocinnamic acid, Ka = 5.13×105
6. What is the hydronium ion concentration of a 0.200 M solution of 3,6-dinitrophenol (Ka = 7.1×106)?
A. 8.4×104 M
B. 1.2×103 M
C. 2.7×103 M
D. 6.0×103 M
E. 8.4×103 M
7. The solubility of PbBr2 in pure water at 20 °C is 0.884 g/100 mL. What is Ksp for lead bromide at this temperature?
8. A 5.00 g sample of a metal is heated to 100.00 °C and placed in a perfectly insulated container holding 20.00 g of water at 25.00 °C. After a few minutes the tmperature of the metal and the water are 26.69 °C. What is the specific heat (in units of J/g·K) of the metal? (specific heat of water = 4.184 J/g·K)
9. Eight people standing on a scale have a total weight of 1118 pounds. To the correct number of significant figures, what is the average weight of the people on the scale?
10. In the following, which is the oxidizing agent?
3 Fe2+ + CrO42 + 8 H+ → 3 Fe3+ + Cr3+ + 4 H2O
11. The principle type of bonding in NaCl is
B. polar covalent
C. van der Waals forces
E. hydrogen bonding
12. The hybrid orbitals whose angles to one another are 180° are
13. Which of the following is not an electrolyte when dissolved in water?
A. sodium chloride
C. sulfuric acid
D. potassium hydroxide
E. bicarbonate of soda
14. What is the oxidation number of I in KIO4?
15. According to Le Chatelier's Principle, which of the following would shift the equilibrium reaction shown below to the right?
2 F2(g) + Si(s) ⇔ SiF4(g) ΔH = –1614 kJ/mole
A. increase the temperature
B. increase the volume
C. add SiF4
D. add Si
E. add F2
16. What is the wavelength (in meters) of light that corresponds to an energy of 1.00×10–5 J?
17. Which of the following would you expect to have the highest boiling point?
18. Combustion of 1.000 g of a pure material in oxygen produced 1.782 g of carbon dioxide and 0.729 g of water and nothing else. What is the ratio of carbon to oxygen in the original molecule?
19. What is the correct equilibrium mass action expression for the following reaction?
Ca(HCO3)2(s) ⇔ CaO(s) + 2 CO2(g) + H2O(g)
20. A compound has a per cent composition of 40.81 % C, 6.17 % H, 43.40 % O, and 9.52 % N. What is the empirical formula of this compound?
21. When the following equation is balanced and the coefficient of Mo24O37 is 1, the coefficient of KMnO4 is
Mo24O37 + KMnO4 + H2SO4 → MoO3 + MnSO4 + K2SO4 + H2O
22. A chemical company sells 99.99% pure mercury at $32.80 for 50.00 g. The density of mercury is 13.546 g/mL. What is the price of mercury in dollars per mL?
23. A sample of hydrated calcium pyrophosphate weighing 1.912 g is heated until all of the water is driven off. The residue, anhydrous calcium pyrophosphate (molar mass = 254.10 g/mol) weighs 1.412 g. The formula for hydrated calcium pyrophosphate is Ca2P2O7·XH2O, X is
24. A 0.250 M solution of K2Cr2O7 (molar mass = 294.21 g/mol) has a density of 1.050 g/mL. What is the molality of this solution?
A. 0.238 m
B. 0.250 m
C. 0.256 m
D. 0.263 m
E. 70.0 m
25. The mass percent of lead in lead metavanadate, Pb(VO3)2, is
A. < 30.00 %
B. 30.00 % – 39.99 %
C. 40.00 % – 49.99 %
D. 50.00 % – 60.00 %
E. > 60 %
26. The density of a gas at 91.45 °C and 608 torr is 1.90 g/mL. What is the molar mass of this gas?