①先把铂丝灼烧到与原来的火焰颜色相同,再蘸取被检物质
②钾的火焰颜色,要透过蓝色钴玻璃观察 ③ 每次实验后,要用盐酸把铂丝洗净
④最好选择火焰颜色较浅的煤气灯 ⑤也可以用光洁无锈的铁丝代替
A.仅④不正确 | B.仅③不正确 | C.仅②不正确 | D.全部正确 |
同类型试题
y = sin x, x∈R, y∈[–1,1],周期为2π,函数图像以 x = (π/2) + kπ 为对称轴
y = arcsin x, x∈[–1,1], y∈[–π/2,π/2]
sin x = 0 ←→ arcsin x = 0
sin x = 1/2 ←→ arcsin x = π/6
sin x = √2/2 ←→ arcsin x = π/4
sin x = 1 ←→ arcsin x = π/2
y = sin x, x∈R, y∈[–1,1],周期为2π,函数图像以 x = (π/2) + kπ 为对称轴
y = arcsin x, x∈[–1,1], y∈[–π/2,π/2]
sin x = 0 ←→ arcsin x = 0
sin x = 1/2 ←→ arcsin x = π/6
sin x = √2/2 ←→ arcsin x = π/4
sin x = 1 ←→ arcsin x = π/2