成都市近年来常常发生“毒奶粉”事件。劣质奶粉制造商为牟取暴利，大大降低了奶粉中蛋白质的含量，导致食用这种奶粉的众多婴幼儿严重营养不良乃至死亡。

为了测定某牛奶样品中蛋白质的含量，现采用“盖尔达法”分解其中的蛋白质。其原理是把蛋白质中的氮元素完全转化为氨气（化学式为NH₃），再用稀硫酸吸收氨气，反应的化学方程式为：2NH₃+H₂SO₄=== (NH4)₂SO₄

现取该奶粉样品100g，用“盖尔达法”分解其中的蛋白质，产生的氨气用7.5g溶质质量分数为19.6%的稀硫酸恰好完全吸收。计算并回答下列问题：

（1）产生氨气的质量是多少？（计算结果精确到0.01，下同）

（2）含氮元素的质量多少？

（3）该奶粉中氮的含量是否达到了国家规定的标准。（奶粉中蛋白质的含量国家标准为：每100g婴幼儿奶粉中含12g~25g。蛋白质含氮元素的质量分数为16%）

When President Obama took the stage here Wednesday to address a community--and a nation-- traumatized by Saturday’s shooting rampage in Tucson, Arizona, it invited comparisons to President George W. Bush’s speech to the nation after the attacks of Sept. 11, 2001, and the memorial service President Bill Clinton led after the bombing of a federal office building killed 168 people in Oklahoma City in 1995. But Mr. Obama’s appearance presented a deeper challenge, reflecting the tenor of his times. Unlike those tragedies which, at least initially, united a mournful country and quieted partisan divisions--this one has, in the days since the killings, had the opposite effect, inflaming the divide.
It was a political reality Mr. Obama seemed to recognize the moment he took the stage. He directly confronted the political debate that erupted after the rampage, asking people of all beliefs not to use the tragedy to turn on one another. He called for an end to partisan recriminations, and for a unity that has seemed increasingly elusive as each day has brought more harsh condemnations from the left and the right. It was one of the more powerful addresses that Mr. Obama has delivered as president, harnessing the emotion generated by the shock and loss from Saturday’s shootings to urge Americans "to remind ourselves of all the ways that our hopes and dreams are bound together. \