General Chemistry First Exam

Magnesium metal (0.100 mol) reacted with excess hydrochloric acid. How many liters of hydrogen gas, measured at STP, are produced? Mg(s) + 2HCl(aq) -> MgCl2(aq) + H2(g) 0.1 mol * 1 mol H2 / 1 mol Mg = 0.05 mol H2 V = nRT/P = (0.05 mol)(0.0821 L atm/mol K)(273 K) / 1 atm = 1.12 L **Conditions at STP are:** A. 25 K, 1 atm B. 273.15 K and 760 torr C. 0 K and 1 atm D. 273.15 K and 1 atm E. 0°C and 760 atm **Which of the following relationships is incorrect with regard to electromagnetic radiation?** A. longer wavelength = higher energy B. higher frequency = higher energy C. none of these D. all of these E. longer wavelength = lower frequency **6. A sample of a gas at 0.50 atm and 373 K occupies 2.0 L. What pressure (atm) is necessary to cause the gas to occupy 0.50 L at the same temperature?** P1V1 = P2V2 0.50 atm * 2.0 L = P2 * 0.50 L P2 = 2.0 atm **When balancing the given reaction in acidic medium, the coefficients a, b, c, and d respectively, are:** 2aBr- (aq) + bMnO4-(aq) -> cBr2(l) + dMn2+(aq) A. a = 10, b = 1, c = 5, and d = 2 B. a = 1, b = 2, c = 1, and d = 1 C. a = 6, b = 10, c = 3, and d = 10 D. a = 2, b = 5, c = 1, and d = 5 E. a = 6, b = 4, c = 4, and d = 6 **8. Which of the following electron configurations corresponds to an excited state?** A. 1s²2s²2p⁶ B. 1s²2s²2p⁴3s¹ C. [Ar]4s¹3d⁵ D. 1s²2s²2p⁶3s²3p⁶ E. 1s²2s²2p⁶3s²3p⁶4s¹ **9. Which of the following sets of quantum numbers are not allowed?** A. n = 3, l = 3, ml = 0, ms = +1/2 B. n = 4, l = 3, ml = 2, ms = -1/2 C. n = 4, l = 1, ml = 1, ms = +1/2 D. n = 2, l = 1, ml = 0, ms = -1/2 E. n = 1, l = 0, ml = 0, ms = -1/2 **10. Which of the following is the largest ion?** 11. How many electrons in an atom can have n = 5, l = 3? A. 2 B. 6 C. 10 D. 14 E. 18 12. Each electron in an atom has a unique set of four quantum numbers. This observation is credited to: A. Pauli B. Mendeleev C. Bohr D. Heisenberg E. Hund 13. A 0.650 gram sample of oxygen occupies 1.00 L at 0.5 atm. The gas is then cooled. At what temperature (in Celsius degrees) would the gas occupy 0.5 L at 0.25 atm? (Atomic weight: O = 16.00). A. -215 B. -125 C. -153 D. -196 E. -198 14. Which of the following atoms would experience the greatest energy loss upon gaining an electron? A. N B. Li C. Mg D. Cl E. Na 15. The energy required to excite the hydrogen electron from level n = 1 to n = 2 is: A. 1.216 x 10^-8 J B. 2.116 x 10^-7 J C. 7.621 x 10^-7 J D. 1.216 x 10^-6 J E. 1.216 x 10^-11 J 16. The oxidation state of Mn in the KMnO4 compound is: A. +1 B. +2 C. +5 D. +6 E. none of the above 1. How many grams does 4.00 moles of H2O weigh? (Atomic masses: O = 16; H = 1) A. 4.00 g B. 4.50 g C. 18.0 g D. 72.0 g E. 144.0 g Solution: 4.00 mol H2O * 18 g/mol = 72 g 2. How many grams of sodium chloride are dissolved in 50.0 mL of 1.50 M solution? A. 117 g B. 4.38 x 10^3 g C. 0.00324 g D. 23.4 g E. 4.38 g Solution: moles NaCl = 1.5 mol/L * 0.050 L = 0.075 mol mass NaCl = 0.075 mol * 58.44 g/mol = 4.38 g 3. Consider the following (balanced) combustion reaction. If 16 g of CH4 are consumed, what is the amount of H2O produced, in g? CH4 + 2O2 -> CO2 + 2H2O MW CH4 = 16 g/mol MW H2O = 18 g/mol 16 g CH4 * (1 mol CH4 / 16 g CH4) * (2 mol H2O / 1 mol CH4) * (18 g H2O / 1 mol H2O) = 36 g H2O 4. In an acid-base titration, if 25.0 mL of 0.107 M HCl required 17.00 mL of KOH solution for exact neutralization, what is the molarity of the KOH solution? A. 0.1070 B. 1.574 C. 3.148 D. 0.001573 E. 1.574 x 10^-1 Solution: M1V1 = M2V2 (0.107 M)(25.0 mL) = M2(17.00 mL) M2 = 0.157 M 5. The formula for Chromium(III) chloride is: A. CrCl2 B. CrCl3 C. Cr2Cl3 D. Cr3Cl3 E. Cr2Cl20