现有浓度均为0.01mol•L^﹣1的下列溶液：①H₂SO₄   ②CH₃COOH  ③NaOH   ④Na₂CO₃

请回答下列问题：

（1）已知：T℃，K_W=1×10^﹣13，则T℃____ 25℃（填“＞”、“＜”或“=”），

T℃时，0.01mol•L^﹣1的NaOH溶液的pH=____ ．

（2）①②③④四种溶液中由水电离出的OH^﹣浓度由大到小的顺序是（填序号）____ ．

（3）将装有适量0.01mol•L^﹣1Na₂CO₃溶液（滴有2滴酚酞）的试管，分别进行如图操作：

（i） 说明滴有酚酞的Na₂CO₃溶液显红色的原因　____ （用离子方程式表述）．

（ii） 烧杯中加入NH₄NO₃晶体后，甲试管中溶液红色变浅，下列判断正确的是____ ．

a．水解反应为放热反应          b．水解反应为吸热反应

c．NH₄NO₃溶于水时放出热量    d．NH₄NO₃溶于水时吸收热量

（iii） 乙中观察到的现象是____ ．

（iv） 丙中产生红褐色沉淀同时冒出无色气泡，写出该反应的离子方程式　____ ．

    I went hiking to a mountain with my friends last summer． It was a good trip at the beginning but something unexpected happened on the half way．

    One of my friends, Mike, suddenly felt a terrible pain in his stomach and he couldn't move any further． Nobody knew what to do． One girl tried to call her mum with her mobile phone but there was no signal in the mountain area． Luckily I brought medicine with me． After Mike took some, he felt much better． We walked on, and then we all enjoyed ourselves on the top of the mountain.