题干

碳酸亚铁(白色固体,难溶于水)是一种重要的工业原料,可用于制备补血剂乳酸亚铁,也可用作可充电电池的电极。某研究小组通过下列实验,寻找利用复分解反应制备FeCO3的最佳方案:

实验

试剂

现象

滴管

试管

0.8 mol/L FeSO4溶液

(pH=4.5)

1 mol/L Na2CO3溶液

(pH=11.9)

实验Ⅰ:立即产生灰绿色沉淀,5min后出现明显的红褐色

0.8 mol/L FeSO4溶液

(pH=4.5)

1 mol/L NaHCO3溶液

(pH=8.6)

实验Ⅱ:产生白色沉淀及少量无色气泡,2min后出现明显的灰绿色

0.8 mol/L (NH4)2Fe(SO4)2

溶液(pH=4.0)

1 mol/L NaHCO3溶液

(pH=8.6)

实验Ⅲ:产生白色沉淀及无色气泡,较长时间保持白色

上一题 下一题 0.0难度 选择题 更新时间:2017-03-04 06:40:44

答案(点此获取答案解析)

同类题2

阅读理解

A

    “My wife of 24 years, Marie Roberts, was raised in New York City, worked in the fashion industry, and never got her hands dirty,” said Keith Roberts. “Then, nine years ago, I wanted to move to Florida and reconnect to my country life, but how would I inspire(激发)the same feeling in, well, a city woman? I brought her a two-month-old potbellied pig.”

    At first sight, Marie, then 46, was smitten. So soon she took in another abandoned(遗弃)pig. And thus began Sugarloaf Mountain Farm, her animal shelter in central Florida. With the couple's two children grown up, these animals would now be Marie's babies.

    The Farm now has 300 rescues, from alpacas to donkeys, each with its own story. “A gentleman had a litter of eight pigs, and all but one died,” says Marie. “She weighed one pound and suffered great pain. For three weeks straight, I fed that baby every hour, day and night, seldom sleeping.” Till now, Marie still gets five to ten requests a day to save animals and has to turn most down. “If she can't rescue the animal, she works with that person to find a solution,” Keith says. “She's not only saving animals; above all, she's giving their owners peace of mind.”

    “A woman called from her nursing home,” Marie remembers. “Her pigs would be abandoned if she couldn't find a suitable home. 'I only have a few months, and I need to know that they'll be safe,' she said.” So Marie drove three hours and got them. Soon after, Marie received a note from the woman's daughter. “Dear Marie,” she wrote. “My mom went peacefully, as she went knowing that they are forever loved. Thank you for being Mom's angel.”

    “She is a ball of energy,” Keith adds. “A few times she's gone so far in some situations, like when she locked herself in the chicken coop(鸡舍). I found her sitting in it with ten chicks nestled in her lap.” That is exactly what you'd expect from a true mother hen.