把13枚棋子放入4个小方格里,至少有一个小方格内有______枚棋子.
13÷4=3(个)…1(个),
3+1=4(个);
答:至少有一个小方格内有4枚棋子.
故答案为:4.
NA表示阿伏加德罗常数,下列判断正确的是 ( )
A.在18 g18O2中含有2NA个氧原子
B.1 mol H2与1 mol Cl2反应生成NA个HCl分子
C.1 mol Ca变成Ca2+时失去的电子数为2NA
D.电解精炼铜时,若阴极得到电子数为2NA个,则阳极质量减少64 g
开放作文。
请根据下面提示,写一篇短文。词数不少于50。
In your English class, your teacher shows you the following picture. You are asked to describe the
picture and explain how you understand it.
参考词汇:鸵鸟 ostrich 蜗牛 snail
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