24．人体中含量最多的元素与地壳中含量最多的金属元素形成的化合物的化学式__________。
23．人类生命活动离不开的气态单质是____________、液态氧化物是________。空气质量指标中含量二氧化硫过多会引起__________。
22．有20g氢气和氧气的混合气体，点燃爆炸后得到18g水，氧气已经完全反应，则原混合气体中氢气的质量可能为····························································································································· [ ]
A．8 g B．4 g C．16 g D．1 g
21．t℃时，向饱和溶液中加入一定量的水后，下列有关该溶液的叙述正确的是····· [ ]
A．仍为饱和溶液 B．溶质的质量变小
C．溶质的溶解度不变 D．溶质的质量分数不变
20．在配制一定溶质质量分数的溶液时，正确的操作顺序是·································· [ ]
A．计算、称量、量取、溶解 B．溶解、称量、量取、计算
C．计算、溶解、称量、量取 D．溶解、计算、称量、量取
19．将氮气、一氧化碳、二氧化碳的混合气体先通过足量澄清的石灰水、再通过足量灼热的氧化铜，最后剩余气体是····························································································································· [ ]
A．氮气 B．二氧化碳 C．一氧化碳 D．二氧化碳和氮气
18．在氧化－还原反应CO+CuOCO2+Cu中，氧化剂是·························· [ ]
A．CuO B．C C．CO D．Cu
17．有100克溶质质量分数为5%的食盐溶液，若将其溶质的质量分数提高到20%，则采取的措施是 [ ]
A．蒸发55克水 B．蒸发75克水 C．加入5克固体食盐 D．加入15克固体食盐
16．在氢气还原氧化铜的实验中，进行如下操作：①加热②停止加热③通入氢气④停止通入氢气。下列操作顺序正确的是 [ ]
A．③①④② B．①③②④ C．③①②④ D．①③④②
15．大气中的臭氧层能吸收来自太阳辐射的紫外线，保护地球上的生物。有关臭氧(O3)
的下列说法中，错误的是······················································································· [ ]
A．臭氧和氧气是同一种物质 B．每个臭氧分子中有3个氧原子
C．臭氧由氧元素组成 D．臭氧中氧元素是游离态
CO2+Cu中，氧化剂是·························· [ ]