SPLA an unknown acid whose equivalence point is at pH7 suggests that weak acid b
ID: 699017 • Letter: S
Question
SPLA an unknown acid whose equivalence point is at pH7 suggests that weak acid because the equivalence point of all strong acids is below pH 7 This is a This is a strong acid because the equivalence point of all strong acids is pH-7 b. d. This is actually pure water 22. Which of the following mixtures would make a good buffer? a. Mixing equal amounts of HNO, and NO, b. Mixing equal amounts of HNO, and NO c. Mixing equal amounts of HNO, and NO d. Mixing equal amounts of HNO, and NO, 23. If a reaction is spontaneous: The free energy change must be positive a. b. c. d. 24. Entropy change: The free energy change must be negative The reaction must be exothermic The reaction must be endothermic . a. Is positive when disorder has increased in a system b. Is positive when disorder has decreased in a system 25. The enthalpy change of a reaction: Is always negative at equilibrium Is always positive at equilibrium a. b. c. Is equal to the entropy change at equilibriunm d. None of the above are true 26. The entropy of a pure crystalline solid: a. Is zero at zero Kelvin b. Is zero at equilibrium c. Both a and b are true d. Both a and b are false 27. During melting: a. The free energy change is zero b. The entropy change is zero c. The enthalpy change is zero d. All of the above are true 28. Potential is: a. b. c. d. Electron per charge Energy per mol Charge per mol None of the above 29. An oxidation half-reaction: a. Will always show the electrons on the reactant side b. Will always show the electrons on the product side c. May show electrons on one side or another depending on the actual half-reaction d. None of the above is trueExplanation / Answer
21) This is true only when titrating a strong acid with a strong base. At the endpoint of the titration when the number of mols acid (HA) and base put into solution are the same. Therefore, at endpoint [HA] = [ROH] and [H+] = [OH], and pH is therefore 7. Answer is b
22) A buffer is an aqueous solution of a mixture of a weak acid and its conjugate base or weak base and its conjugate acid. Here HNO2 is a weak acid, comparing with HNO3 and the conjugate base of HNO2is NO2-. Therefore, the answer is b
23) For a spontaneous process taking place at constant temperature and pressure, the free energy change must be negative. Answer is b
24) Entropy is a measure of the disorder of the system. Therefore entropy change is positive when disorder has increased in the system. Here answer is a
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