题目

C Cancun is a seaside town in Mexico, where most tourists come here to enjoy the beach, water sports and night life. In fact, it is so modern and Americanized that you might think you were in southern California or Florida. But just a short two-hour hike from the town lie the ruins of the city of Chichen-Itza, one of the capitals of the lost Maya（玛雅）civilization. The center of the ruins of this city is the pyramid of El Castillo. The ancient Mayan religious people climbed this pyramid during festival to honor the Sun god. Tourists today climb it to view the architectural achievements o下列反应在210℃达到平衡：      PCl5(g)PCl3(g)+Cl2(g)    △H ＞0      K＝1           ①      CO(g)+Cl2(g)COCl2(g)   △H ＜0      K＝5×104       ②      COCl2(g)CO(g)+ Cl2(g)   △H ＞0                                ③ （1）化学平衡常数K表示可逆反应的进行程度，K值大小与温度的关系是：温度升高，K值_______     ___________（填一定增大、一定减小、或可能增大也可能减小）。 （2）根据反应①的平衡常数K的表达式，平衡时，下列等式必定成立的是             A．c(PCl5) = c(PCl3)= c(Cl2)=1  B．c(PCl5)= c(PCl3)·c(Cl2)=1  C．c(PCl5)= c(PCl3)·c(Cl2)      反应②和反应③的K值表达式          (填“相同”或“不同”)   （3）降低Cl2浓度，反应③的K值    ____   (填“增大”、“减少”或“不变”)。