Chemistry Second Exam 2021

General Chemistry Second Exam Chemistry Department Time: 60 min. Name:__________________________ Registration Number:_______________ Instructor:______________________ Seat No:_________ Day/Time:__________ Answer Sheet K = °C+273, 1atm = 760mmHg, R = 0.082057L.atm/(K.mol) = 8.314J/(K.mol), L.atm = 101.3J, Nₐ = 6.022x10²³, h= 6.63x10⁻³⁴ J.s, Rн=2.18x10⁻¹⁸ J, c = 3x10⁸ m/s, PV=nRT, u_rms = √(3RT/M), KE = -3/2 RT = Nₐ(½mu²), ∆E = ∆H - P∆V, ∆E = q + w, c = λν, E=hv, E_n = -Rн(1/n²), λ=h/(mu), a b (c) d e 9. a (b) c d /e a (b) c d e 10. a (b) c d e a b c (d) e 11. a b (c) d e a b c d (e) 12. a (b) c d e a /b c (d) e 13. a b (c) /d e (a) b c d e 14. /a b (c) d e a b c (d) /e 15. a b (c) d e a b (c) d e 16. a b (c) d e n = m/MM n = 0.018 P = nRT/V n = PV/RT = 1 x 0.401 / 0.082057 x 273.15 Determine the molar mass of a gas if 0.401 L weighs 1.55g at STP? a) 69.3 g/mol b) 94.5 g/mol (c) 86.6 g/mol d) 53.3 g/mol e) 43.3 g/mol Pₑ = Pн2 + Pн2O → Pн₂ = 988 - 118 = 870 mm hg* In a reaction of calcium metal with water, the volume of hydrogen gas collected at 50°C and pressure of 988 mmHg is 441 mL. What is the mass (in grams) of the hydrogen gas obtained? The vapor pressure of water at 50°C is 118 mmHg. (Molar mass of H₂ = 2.016 g/mol ) a) 0.0436g (b) 0.0384g c) 0.0190g d) 0.0242g e) 0.0488g n = PV/RT = Calculate the mass of calcium (in g) that must be dissolved in sulfuric acid in order to obtain 500mL of hydrogen gas at 20°C and 770 mmHg? (Molar mass of Ca = 40.08 g/mol ) Ca(s) + H₂SO₄(aq) → CaSO₄(s) + H₂(g) a) 1.38 g b) 0.0425 g c) 1.24 g (d) 0.84 g e) 1.18 g n=PV/RT = 770 x 0.500/ 0.082057K (20 + 273) 4) What is the kinetic energy of a mole of CO₂ at 200K (in kJ)? a) 200 kJ b) 4.14x10⁻²⁴ kJ c) 2.5x10⁻³ kJ d) 0.200 kJ (e) 2.49 kJ [Formulas with numbers written next to them for 4)] KE = ½ mv² 3/2 R (T) k = R/Na = L.atm Which of the following is a wrong statement? a) H₂ gas behaves more ideally than CO₂ gas b) CO₂ (44 g/mol ) effuses faster than N₂(g) (28 g/mol ) at STP c) At the same temperature molecules of a gas with low molar mass have higher average velocity than heavier molecules (d) Average kinetic energy depends only on temperature. e) Real gases behaves as ideal gases at low pressure and high temperature. P₁V₁ = P₂V₂ u_rms = √(3RT/MM) = √ 6) Calculate the root mean square velocity (u_rms) in (m/s) of CO₂ molecules in a sample of CO₂ gas at 1.0 °C. [molar mass of CO₂ = 44.0 g/mol ] (a) 394 b) 44.0 c) 1.24 d) 39.2 e) 12.5 [Formulas with numbers written next to them for 6)] 7) A gas is allowed to expand, at constant temperature, from a volume of 3.0 L to 8.0 L against external pressure of 1.10 atm. If the gas absorbs 350 J of heat from the surroundings, then ΔE in J: q = +350J a) -345 b) +207 c) -907 (d) +345 e) -207 ΔE = ΔH - PΔV W= -PΔV ΔE = q+w -5.5 ΔV > 0 W=- 8) Consider the combustion of isooctane C₈H₁₈ (Molar mass = 114 g/mol ): 2 C₈H₁₈(l) + 25 O₂ → 16 CO₂ + 18 H₂O(l) ΔH= -10930 kJ Calculate the energy released when 105 g of isooctane are combusted in excess oxygen? a) 2.19x10⁴ kJ b) 1.01x10⁴ kJ (c) 5.03x10³ kJ d) 2.52x10³ kJ e) 2.01x10⁴ kJ [Formulas with numbers written next to them for 8)] ΔH 2 → -10930 ΔE = q+w DH=ΔH ΔH =H₁ 9) When 500.0 mL of 0.400 M Ca(NO₃)₂ is added to 500.0 mL of 0.800 M NaF, CaF₂ precipitates, as shown in the net ionic equation below. The initial temperature of both solutions is 20.00 °C. Assuming that the resulting solution has a mass of 1000.00 g and a specific heat of 4.18 J/(g.°C) calculate the final temperature of the solution. Ca²⁺(aq) + 2F⁻(aq) → CaF₂(s) ΔH° = -11.5 kJ a) 18.90 °C (b) 20.00 °C c) 19.45 °C d) 20.55 °C e) 21.10 °C [Hand drawn diagram below 9] Ca(NO₃)₂ + NaF 500 mL 500 mL 0.400M 0.8M 20 °C m_s= 1000 g S=418