亚磷酸（H₃PO₃）是二元酸，H₃PO₃溶液存在电离平衡：H₃PO₃⇌H⁺+H₂PO₃^﹣．亚磷酸与足量NaOH溶液反应，生和Na₂HPO₃．

（1）①写出亚磷酸与少量NaOH溶液反应的离子方程式　____ ．

②根据亚磷酸（H₃PO₃）的性质可推测Na₂HPO₃稀溶液的pH____ 7（填“＞”、“＜”或“=”）．

③某温度下，0.1000mol•L^﹣1的H₃PO₃溶液中c （H⁺）=2.5×10^﹣2 mol•L^﹣1，除OH^﹣之外其他离子的浓度由大到小的顺序是　____ ，该温度下H₃PO₃电离平衡的平衡常数K=____ ．（H₃PO₃第二步电离忽略不计，结果保留两位有效数字）

（2）亚磷酸具有强还原性，可使碘水褪色，该反应的化学方程式____ ．

（3）电解Na₂HPO₃溶液也可得到亚磷酸，装置示意图如下：说明：阳膜只允许阳离子通过，阴膜只允许阴离子通过．

①阴极的电极反应式为____ 　．

②产品室中生成亚磷酸的离子方程式为　____ ．

完形填空

    Each morning during fifteen- minute bath, I determined to cultivate a b+添加知识点ig, happy smile. I found out it had to be an honest-to-goodness smile from down deep 1 , an outward expression of happiness from within!

        Let's see how the smile muscles 2 me during the day. I would think of the things I had to be 3 for, work up a big smile and then enter. It 4 people when I passed them on the street to give them a 5 smile. Give every living soul you meet the best smile you have 6 smiled in your life, and see how much better you feel and look. It's one of the best ways to 7 worrying, and start living. When I began to do this, I found I became more welcome everywhere.