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final01a

# final01a - Formulas and Constants Thermochemistry Hrxn = n...

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Formulas and Constants Thermochemistry H ° rxn = Σ n H ° (products) - Σ n H ° (reactants) H ° rxn = Σ n H ° (enthalpies of bonds broken) - Σ n H ° (enthalpies of bonds formed) q = mC s (T F ° T I ) Properties of Electromagnetic Radiation E = hc/ λ = h ν λν = c DeBroglie Relationship λ = h/(mv) Potential Energy of Two Interacting Charges E = k (Q 1 Q 2 )/d Physical Constants Avogadro±s Number N = 6.022 × 10 23 Planck±s Constant h = 6.626 × 10 -34 J-s Speed of Light c = 3.00 × 10 8 m/s Rydberg±s Constant R H = 1.10 × 10 7 m -1 Charge of an Electron e = 1.602 × 10 -19 C Temperature Conversions K = 273 + ° C STP 273 K and 1 atm 1 mL = 1 cm 3

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1. [7.5 points] How many electrons, protons and neutrons does 43 Ca 2+ have? (a) 20 protons, 23 neutrons and 18 electrons (b) 23 protons, 20 neutrons and 21 electrons (c) 20 protons, 23 neutrons and 20 electrons (d) 20 protons, 18 neutrons and 23 electrons (e) none of the above are correct 2. [7.5 points] What is the formula of chromium (III) oxide? 3. [7.5 Points] What is the empirical formula of the ionic compound that forms between calcium and sulfur? 4. [7.5 points] What is the quantity of Fe 2 O 3 that will be produced if 5.00 g of FeS 2 is reacted with 11.0 g of oxygen according to the following reaction: 4 FeS 2 (s) + 11 O 2 (g) 2 Fe 2 O 3 (s) + 8 SO 2 (g) 5. [7.5 Points] When 27.3 g of Fe powder is completely burned in air, an iron oxide is produced. The mass of the iron oxide should be: (a) less than 27.3 g because mass is lost on burning (b) equal to 27.3 g because matter is conserved in a chemical reaction (c) greater than 27.3 g because oxygen has been added to the iron (d) equal to 43.3 g which is equal to the initial mass of Fe plus the atomic mass of oxygen
6. [7.5 points] When a sample of ammonium nitrate dissolves in 100 g of water, the temperature changes from 25 ° C to 15 ° C. For this process: (a) H is positive and the process is endothermic (b) H

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final01a - Formulas and Constants Thermochemistry Hrxn = n...

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