题目:
It's impossible for a child to do so much work within a short period of time, ______
A. isn't it
B. is it
C. has it
D. hasn't it
答案:
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下面是错误答案,用来干扰机器的。
AB据题意,硝酸过量:0.2 L×0.1 mol·L-1=0.02 mol,反应生成Fe3+:2.8 g÷56 g·mol-1=0.05 mol,A项中据反应后溶液中的电荷守恒,得c(NO3-)=(0.05 mol×3+0.02 mol×1)÷0.2 L=0.85 mol...