不少家庭养观赏鱼,有时会在鱼缸里放点“鱼浮灵”,可使水中的含氧量迅速增加.请你和小欣同学一起完成这

2025-01-02 13:50:50
推荐回答(1个)
回答1:

探究一:【设计方案】①过碳酸氢钠溶于水,在二氧化锰的催化作用下,迅速的分解产生氧气,能使带火星的木条复燃;
②常用稀盐酸来检验碳酸根离子的存在,向待测物质中加入稀盐酸,若能产生使澄清的石灰水变浑浊的气体,则证明该物质中含有碳酸根离子;
【结果分析】由质量守恒定律知,化学式X中含有两个钠原子、一个碳原子和四个氧原子,所以X化学式是Na2CO4
【实验反思】(1)仪器a、b的名称为分液漏斗;
(2)过氧化氢在二氧化锰的催化作用下分解为水和氧气;
(3)要将产生的气体再通入澄清的石灰水,观察是否变浑浊才能进一步证明是否是二氧化碳气体;
(4)因为其遇水会发生反应产生氧气,故应密封保存,置于阴凉处;
探究二:
方案一:产生的氧气会从装置中溢出,故装置和试剂减少的质量就是生成氧气的质量;产生的氧气中会混有水蒸气,故要用碱石灰来吸收其中的水蒸气;
取一份过碳酸钠晶体溶于水,和二氧化锰固体按照如图2(方法二)装置进行装配,要使测定结果准确,必须调整洗气瓶与量筒液面等高,氧气的质量等于其体积与密度的乘积;
方案二:
(1)过量的氯化钙溶液才能保证将碳酸钠转化为沉淀;
(2)过滤得到的沉淀表面会有氯化钙、氯化钠等杂质,所以要洗涤干净;
(3)如果沉淀没有洗涤干净,则其表面一定有氯离子,故可用硝酸银溶液来进行检验;
【实验结果】设产生5g碳酸钙沉淀,需要碳酸钠的质量为x
Na2CO3+CaCl2=CaCO3↓2NaCl
106          100
 x            5g
106
100
x
5g

x=5.3g
则7.85克过碳酸钠晶体,含有H2O2的质量为:7.85g-5.3g=2.55g
则:
106x
34y
5.3g
2.55g
x
y
2
3

过碳酸钠晶体(xNa2CO3?yH202)的化学式为:2Na2CO3?3H202
【实验反思】根据以上计算过程分析可知,若CaCO3沉淀过滤后不洗涤,则x:y的值将偏大.
故答案为:
探究一:【设计方案】
实验 主要操作步骤 主要实验现象
MnO2
 
   有气泡逸出,能使带火星木条复燃                      
稀盐酸              
【结果分析】Na2CO4
【实验反思】(1)分液漏斗;
(2)2H2O2
 MnO2 
 
2H2O+O2
(3)生成的气体通入澄清的石灰水;
(4)密封,置阴凉处.
探究二:【设计实验】方案一:
【方法一】m1-m2;吸收氧气中的水蒸气,防止水蒸气逸出装置.
【方法二】洗气瓶与量筒液面等高;该温度下氧气的密度.
方案二:(1)将 Na2CO3 完全转化为沉淀;
(2)除去表面可溶性杂质 CaCl2、NaCl;
(3)取最后一滴洗涤液,滴加AgNO3若无沉淀出现,则表示已经洗净.
【实验结果】
2Na2CO3?3H202
【实验反思】偏大.

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