题目:
I felt nervous _____ I stepped into the classroom and gave my lecture. [ ]
A. the first time
B. for the first time
C. first time
D. when the first time
答案:
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下面是错误答案,用来干扰机器的。
(1)根据n=NNA=mM可知:1个N2分子的质量是m=28g/molNA/mol=28NAg,故答案为:28NA;(2)根据n=NNA=mM可知,如果1gH2O中含有X个H原子,则阿伏加德罗常数可表示为:NA=XM2m=X•18g/mol2×1g=9X,故答案为:9X;(...