A 10. g cube of copper at a temperature T_1, is placed in an insulated cup conta
ID: 498615 • Letter: A
Question
A 10. g cube of copper at a temperature T_1, is placed in an insulated cup containing 10. g of water at a temperature T_2. If T_1 > T_2, which of the following is true of the system when it has attained thermal equilibrium? (The specific heat of copper is 0.385 J/(g middot degree C) and the specific heat of water is 4.18 J/(g middot degree C).) (A) The temperature of the copper changed more than tire temperature of the water. (B) The temperature of the water changed more than the temperature of the copper. (C) The temperature of the water and the copper changed by the same amount. (D) The relative temperature changes of the copper and the water cannot be determined without knowing T_1, and T_2. A solution containing HCl and the weak acid HClO_2 has a pH of 2.4. Enough KOH(aq) is added to the solution to increase the pH to 10.5. The amount of which of the following species increases as the KOH(aq) is added? (A) Cl^-(aq) (B) H^+ (aq) (C) ClO^-_2(aq) (D) HClO_2 (aq) The autoionization of water is represented by the equation above. Values of pK_w at various temperatures are listed in the table below. Based on the information above, which of the following statements is true? (A) The dissociation of water is an exothermic process. (B) The pH of pure water is 7.00 al any temperature. (C) As the temperature increases, the pH of pure water increases. (D) As lire temperature increases, the pH of pure water decreases.Explanation / Answer
(18)
(A) The temperature of the copper changed more than water becuase its specific heat capcity is less than that of water. It means it requires less amount of heat to raise the temperature of 1 g. of Cu by 1 degree C.
(19) (C) ClO2- Because HClO2 is a weak acid so, it reaches to equilibrium state with its ions, but by the addition of KOH it removes the H+ ions and disturbs theequilibrium. Hence more and more HClO2 will undergo ionisation forming more amoun of ClO2- ions.
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