某待测液中可能含有大量Mg²⁺、Cu²⁺、Fe³⁺、K⁺、H⁺、NO₃^﹣、SO₄^2﹣、OH^﹣离子中的一种或几种，现通过下实验进行检验：

①取少量待测液，仔细观察，呈无色；

②向上述待测液中滴加NaOH溶液，先无明显现象，后有白色沉淀生成，

③像上述溶液中加入BaCl₂溶液，无现象．

据此可以判断该待测液中一定大量存在的离子是____，一定不能大量存在的离子是____，不能确定是否存在的离子是____，依次写出（2）中加入氢氧化钠后的离子反应：____，____．

“供给侧改革”是从供给、生产端入手，将发展方向锁定新兴领域、创新领域，创造新的经济增长点。当下供给侧存在如下问题：面向低收入群体为主的供给体系，没有及时跟上国内中等收入群体迅速扩大而变化了的消费结构；供给体系满足多样化、个性化消费的能力相对比较差；有些产业的发展已达到了资源环境承载能力的峰值；企业生产经营成本提高过快，削弱了企业特别是实体经济企业的盈利能力等等。

    The Summer Science Exhibition（展览）is held every year to celebrate the cutting edge of UK science. With more than twenty exhibits of hands-on science and technology and a series of encouraging talks and activities, there's something for everyone. All of our events are free and no booking is required. School groups should let our organizers know ahead of time. Meet the scientists, discover the exciting research and technology they work on and have fun with great hands-on activities.

Opening hours

    The exhibition will be open from Monday, July 2, to Sunday, July 8, 2018. More detailed opening hours will be published here in May 2018.

    Please wait in line to enter the building and pass through security（安全）, particularly during the weekend. If you are planning to attend a talk, please make sure that you leave enough time.

Food and drink

    Take a break at our café which offers a selection of hot dishes, salads, sandwiches, cakes and some soft drinks on the ground floor.

The café is open throughout the exhibition and closes 30 minutes before closing time each day.

    Wheelchair users please speak to a worker if you would like to buy food from the café.

Contact

    If you have any questions before your visit, please keep in touch with us on 020 7451 2242 or at exhibition@royalsociety.org. For schools or colleges, visit our school and college page, or contact education@royalsociety.org.

— Bob, it's getting cold.       take a jacket with you? — All right, Dad.