题干

为了节约林木资源,近几年兴起石头纸.石头纸可用沿海水产养殖中产生的大量废弃贝壳制得。为了测定某种贝壳中碳酸钙的质量分数,取贝壳15克,加入150克7.3%的盐酸溶液,充分反应后,称得剩余物质的总质量为159.72克。(假设贝壳中其它物质不与盐酸反应)有人认为,根据上述实验数据,可按如下方案计算:根据“150克7.3%的盐酸溶液”,得出参加反应的氯化氢质量,然后根据反应原理求得碳酸钙的质量,最后求出贝壳中碳酸钙的质量分数。
(1) 以上方案是否正确?
(2) 计算贝壳中碳酸钙的质量分数。

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(1) 不正确,150克7.3%的盐酸溶液中的氯化氢未完全反应 (2) 贝壳中碳酸钙的质量分数为80%

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    Rob Frenette had problems with bullies(欺辱) at school for eleven years. He was often lonely and scared. When he was fifteen, however, he decided to do something about his problems. He walked into a newspaper office and told them about the bullying. His story went into the newspaper and soon all the TV stations in Canada wanted to talk to him about his experiences. They also wanted to hear his ideas to stop bullying.

    After that, Rob continued his studies at school, but in his free time he helped other people with bullying problems. With a friend Katie Neu, he made a website called www. bullyingcanada. ca. Visitors to the website can find advice, stories and poems about bullying, in both English and French. When people are upset, they can talk on the phone or online to Rob and his team. Every weekend Rob has to answer e-mails to the website. He also speaks to children, teachers and members of government around the country about bullying.

    Rob's most important message is: “When bullies are unkind to you, it isn't your fault (过错、责任). There's nothing wrong with you, so you should try to keep trusting yourself. And remember that people care about your problems. You just have to find those people.”

    One of Rob's ideas is “Blue Day”, a special day for stopping bullying in schools. Students have to wear blue clothes and in class they learn how to stop bullying. More than 150 Canadian schools now celebrate Blue Day, but Rob won't stop until there's a Blue Day in every school in Canada.