实验课上,为检验镁条能否在N2中燃烧,某兴趣小组开展如下探究:
【查阅资料】氮化镁(Mg3N2)是一种淡黄色固体,能和水反应,生成Mg(OH)2和NH3;
【实验步骤】
①将足量白磷在空气中点燃后,迅速伸入钟罩内,塞紧橡皮塞(图1);
②待钟罩内水面不再变化时,向水槽中加水,使水槽中液面与钟罩内液面相平;
③打开橡皮塞,将燃着的螺旋状镁条迅速伸入钟罩内,塞紧橡皮塞(图2);
④待钟罩内水面不再变化时,观察钟罩内壁及表面皿中固体颜色,取少量固体加入水中。
从方框中选择恰当的句子,将对话补充完整。
A—Mr. Black B—Shop Assistant
A: Good morning.
B: Good morning. Welcome! ____
A: Will you show me some T-shirts?
B: Sure. ____
A: Size fourteen.
B: ____
A: White.
B: Here you are. This is the best in our shop.
A: Good. 4. ____
B: Eleven dollars.
A: ____, please. Here's twenty fivedollars.
B: Here's your change. Thank you.