Passage VI

Figure 1 shows how the H2O vapor pressure (the pressure exerted by the H2O vapor in air) varies with the rela­tive humidity (RH) of the air at CTP, which denotes a constant temperature of 25°C and pressure of 101,325 pas­cal (Pa). Figure 2 shows how air density varies with H2O vapor pressure at CTP.

At CTP, the air above an aqueous solution in a closed container has a constant RH. Figure 3 shows, for 3 com­pound, how the RH of the air at CTP in a closed container varies with the percent by mass, of the compound dissolved in the aqueous solution in the container.

Figure 3 adapted from James G Speight, Labge's Handbook of Chemistry, 16th ed. ©2005 by McGraw-Hill, Inc.

39. Consider a 35% by mass aqueous solution of H2SO4 in a closed container. Based on Figures 1-3, if the air above the solution in the container is at CTP, the den­sity of the air will be closest lo which of the following?

Answer and Explanation

Your Answer is

Correct Answer is B

Explanation

According to Figure 3, when the sulfuric acid concentration is 35%, the RH is about 70%; according to Figure 1, when the RH is 70%, the water vapor pressure is about 2100Pa; according to Figure 2, when the pressure is 2100Pa, the air density is about 1175g /m³.