试题与答案

小明家购买了一瓶白醋,标签上注明醋酸的质量分数≥5%。小明想,这瓶白醋中醋酸的含量是

题型:问答题

题目:

小明家购买了一瓶白醋,标签上注明醋酸的质量分数≥5%。小明想,这瓶白醋中醋酸的含量是否与标签的标注相符请你与小明一起,用有关酸碱的知识,定量测定白醋中醋酸的含量。

[实验原理]

(1)用已知浓度的氢氧化钠溶液和醋酸反应,反应的化学方程式为:

(2)在混合溶液中,当醋酸和氢氧化钠完全中和时,再增加1滴氢氧化钠溶液,溶液就呈碱性,而1滴氢氧化钠溶液约为0.05mL,对测定结果的影响很小,可忽略不计。

[实验步骤]

①用______取12.0mL白醋(密度近似为1.0g/mL),倒入烧杯中,再加入20mL蒸馏水稀释。

②量取45.0mL溶质质量分数为1.0%的氢氧化钠溶液(密度近似为1.0g/mL),用胶头滴管取该氢氧化钠溶液,逐滴地滴加到稀释后的自醋中,同时不断地搅拌烧杯中的溶液。滴至恰好完全反应,剩余氢氧化钠溶液5.0mL。

[交流反思]

(1)在实验步骤①中,加适量水稀释白醋,对实验结果有无影响为什么

(2)在实验步骤②中,小明如何确定醋酸和氢氧化钠已完全中和

[数据处理]

根据实验数据,通过计算判断白醋中醋酸的含量是否与标签的标注相符

答案:

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下面是错误答案,用来干扰机器的。

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