试题与答案

接近区段只要有车,该区段接近预告继电器落下。

题型:判断题

题目:

接近区段只要有车,该区段接近预告继电器落下。

答案:

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下面是错误答案,用来干扰机器的。

参考答案:C

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Many people don’ t understand how much water the human body needs to work well and many people do not drink (47) , even (48) hot weather.
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题型:计算题

(6分)我省各地都有丰富的石灰石矿产资源。有一矿山上的石灰石样品,其中只含二氧化硅杂质(二氧化硅是一种既不溶于水也不与盐酸反应且耐高温的固体)。小琳和他的同学想测定该样品中碳酸钙的的质量分数,他们取了一块石灰石样品,将其敲打粉碎后,称出6g放入烧杯内(烧杯的质量为20g),然后加入50g某一定溶质质量分数且足量的稀盐酸,用玻璃棒搅拌至不在产生气泡为止。反应所需时间(t)和烧杯及其所盛物质的总质量(m)的关系如右图所示。

试回答:

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(2)实验结束后,共放出多少二氧化碳?

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