General Science IBDP Chemistry Uncategorized 5. Energetics and thermochemistry HL June 9, 2021 Shveta 0 Comments Energetics and thermochemistry, ibdp chemistry 1.Which combination of ionic charge and ionic radius give the largest lattice enthalpy for an ionic compound? Ionic charge Ionic radius A. high large B. high small C. low small D. low large ABCD2. The lattice enthalpy values for lithium fluoride and calcium fluoride are shown below. LiF(s) ∆Hο = +1022 kJ mol–1 CaF2(s) ∆Hο = +2602 kJ mol–1 Which of the following statements help(s) to explain why the value for lithium fluoride is less than that for calcium fluoride? I. The ionic radius of lithium is less than that of calcium. II. The ionic charge of lithium is less than that of calcium.I onlyII only I and II Neither I nor II 3. Which reaction has the most negative ∆Hο value?LiF(s) → Li+(g) + F–(g) Li+(g) + F–(g) → LiF(s) NaCl(s) → Na+(g) + Cl–(g) Na+(g) + Cl–(g) → NaCl(s)4. Which type of reaction is referred to in the definition of standard enthalpy change of formation?the formation of a compound from its elementsthe formation of a crystal from its ions the formation of a molecule from its atoms the formation of a compound from other compounds 5. What is the correct order of decreasing entropy for a pure substance?gas > liquid > solid solid > liquid > gas solid > gas > liquidliquid > solid > gas 6. Which reaction has the largest positive value of ΔSӨ?CO2(g) + 3H2(g) → CH3OH(g) + H2O(g) 2Al(s) + 3S(s) → Al2S3(s)CH4(g) + H2O(g) → 3H2(g) + CO(g) 2S(s) + 3O2(g) → 2SO3(g) 7. Which is a correct equation to represent the lattice enthalpy of magnesium sulfide?MgS(s) → Mg(s) + S(s)MgS(s) → Mg(g) + S(g) MgS(s) → Mg+(g) + S–(g) MgS(s) → Mg2+(g) + S2–(g)8. Which equation represents a change with a negative value for ΔS?2H2(g) + O2(g) → 2H2O(g) H2O(s) → H2O(g) H2(g) + Cl2(g) → 2HCl(g) 2NH3(g) → N2(g) + 3H2(g) 9. The expression for the standard free energy change of a reaction is given by ΔGӨ = ΔHӨ – TΔSӨ What are the signs for ΔHӨ and ΔSӨ for a reaction that is spontaneous at all temperatures? ΔHӨ ΔSӨ A. + – B. – + C. + + D. – – ABCD10. Which are characteristics of ions in an ionic compound with a large lattice enthalpy value?Large ionic radius and high ionic chargeSmall ionic radius and low ionic chargeLarge ionic radius and low ionic charge Small ionic radius and high ionic charge11. The following reaction is spontaneous only at temperatures above 850°C. CaCO3(s) → CaO(s) + CO2(g) Which combination is correct for this reaction at 1000°C? ΔG ΔH ΔS A. – – – B. + + + C. – + + D. + – – ABCD12. Consider the following information. Compound C6H6(l) CO2(g) H2O(l) ΔHfӨ / kJ mol–1 +49 +394 –286 C6H6(l) + O2(g) → 6CO2(g) + H2O(l) Which expression gives the correct value of the standard enthalpy change of combustion for benzene (l), in kJ mol–1?12(−394) + (−286) −2(49) 12(394) + 6(286) −2(−49) 6(−394) + 3(−286) − (−49) 6(394) + 3(286) − (−49) 13. Which equation represents the lattice enthalpy of magnesium oxide?Mg(s) + O2(g) → MgO(s) Mg2+(g) + O2–(g) → MgO(g) Mg2+(g) + O2(g) → MgO(s) Mg2+(g) + O2−(g) → MgO(s) 14. The ΔHӨ and ΔSӨ values for a reaction are both negative. What will happen to the spontaneity of this reaction as the temperature is increased?The reaction will become more spontaneous as the temperature is increasedThe reaction will become less spontaneous as the temperature is increasedThe reaction will remain spontaneous at all temperaturesThe reaction will remain non-spontaneous at any temperature15. Which reaction has the most negative ∆Hο value?LiF(s) → Li+(g) + F–(g) Li+(g) + F–(g) → LiF(s)NaCl(s) → Na+(g) + Cl–(g) Na+(g) + Cl–(g) → NaCl(s)16. Which equation represents the electron affinity of calcium?Ca(g) →Ca+(g) + e– Ca(g) →Ca–(g) + e– Ca(g) + e– → Ca–(g)Ca+(g) + e– → Ca(g) 17. Which reaction causes a decrease in the entropy of the system?CaCO3(s) → CaO(s) + CO2(g)2H2(g) + O2(g) → 2H2O(l)2C(s) + O2(g) → 2CO(g) 2SO3(g) → 2SO2(g) + O2(g)18. What are the signs of ∆Hο and ∆Sο for a reaction that is non-spontaneous at low temperature but spontaneous at high temperature? ΔHο ΔSο A. – – B. + – C. – + D. + + ABCD
