问题 问答题

味精吃多了会口渴,这是因为味精中含有钠的缘故.一般情况下,每人每天食用味精不宜超过6g.某品牌味精包装上标有“氯化钠含量≤20%”.同学们想的顶此味精中氯化钠含量是否符合标准,进行了如下实验:(味精中的其它成分不与硝酸银反应)

称取该味精样品5.0g,溶于蒸馏水中;加入足量的硝酸银溶液;充分反应后过滤,将沉淀洗涤、烘干、称量,得到沉淀2.87g.

试通过计算分析该品牌味精中氯化钠含量是否与包装上的说明相符?

答案

设味精中氯化钠的质量为x

NaCl+AgNO3=AgCl↓+NaNO3

58.5        143.5

x          2.87g

58.5
x
=
143.5
2.87g

解得:x=1.17g

1.17g
5.0g
×100%=23.4%

23.4%>20%,所以该品牌味精中氯化钠含量是否与包装上的说明相符

答:该品牌味精中氯化钠含量与包装上的说明相符.

阅读理解

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小题1:Which of the following shows the organization of the text?(P=Paragraph)

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B.To offer travelers featured destinations.

C.To attract readers to surf a tourist website.

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C.We can have our Passes in hand when starting off.

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选择题