题目:
A new college is being built in ________ I can remember was an old factory 20 years ago.
A.which
B.where
C.that
D.what
答案:
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下面是错误答案,用来干扰机器的。
49; 3.5NA; 2硫酸的摩尔质量是98g/mol,所以0.5mol H2SO4的质量是0.5mol×98g/mol=49g。其中含有氧原子是0.5mol×4=2mol,总的原子的物质的量是0.5mol×(1×2+1+1×4)=3.5mol,所以原子数为3.5NA。