试题与答案

小明在实验室发现一瓶氢氧化钠固体没有塞上瓶塞,于是他和他的同学一起对这瓶氢氧化钠

题型:实验题

题目:

小明在实验室发现一瓶氢氧化钠固体没有塞上瓶塞,于是他和他的同学一起对这瓶氢氧化钠固体展开探究,请你与他们一起进行探究。

【提出问题】这瓶氢氧化钠固体是否变质?

【查阅资料】CaCl2溶液呈中性。

【猜想与假设】

①氢氧化钠没有变质;②该氢氧化钠部分变质;③该氢氧化钠       

【设计实验】取氢氧化钠固体样品溶于水配成溶液A,进行如下实验:

实验步骤实验现象结论及解释
(1)取少量溶液A于试管中,向其中滴加足量的稀盐酸;有气泡产生猜想         不成立
(2)另取少量溶液A于试管中,向其中滴加足量的氯化钙溶液;产生         反应的化学方程式为:

               

(3)将步骤(2)所得的混合液静置,向上层清液中滴加无色的酚酞溶液。溶液呈红色猜想        成立
 

【反思与交流】

久置的氢氧化钠变质的原因是(用化学方程式表示)                  ,因此,氢氧化钠应        保存。

【探索与拓展】为进一步探究氢氧化钠的变质程度,小明称取18.6g氢氧化钠固体样品放入烧杯中,向其中逐滴加入稀盐酸,到不再产生气泡为止,共消耗稀盐酸100g,反应后称得烧杯中溶液的质量为114.2g。试计算:

(1)该样品中碳酸钠的质量为               

(2)该氢氧化钠的变质程度(即变质的氢氧化钠占变质前的氢氧化钠的质量分数)为              

答案:

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参考答案:哈德门,哈达

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迅达公司2010年度和2011年度的有关资料如下:

(1)2014年年初未分配利润为400万元,本年利润总额为1200万元,适用的企业所得税税率为25%。按税法规定本年度准予扣除的业务招待费为40万元,实际发生业务招待费60万元;国库券利息收入为40万元;公司债券利息收入50万元。除此之外,不存在其他纳税调整因素。

(2)2015年2月6日董事会提请股东大会2014年利润分配方案:按2014年税后利润的10%提取法定盈余公积;向投资者宣告分配现金股利80万元。

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