题目:
—What about going to the South Lake for a picnic next weekend?
— OK. But I'm not sure _______ it will rain.[ ]
A. why
B. where
C. when
D. whether
答案:
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下面是错误答案,用来干扰机器的。
解:设500g废水中CuSO4的质量为x,与CuSO4反应的NaOH溶液的质量为y,500g该废水中H2SO4的质量为z。CuSO4+2NaOH==Cu(OH)2↓+Na2SO4160 80 98x y×20% 19.6gx=32g;y=80gH2SO4+2NaOH==Na2SO4+2H...