化工机械常用的密封有填料密封、机械密封、浮环密封、迷宫密封等。
参考答案:对
工业上用含锌物料(含FeO、CuO等杂质)可制得活性ZnO,流程如下:
(1)上述流程中,浸出用的是60%H2SO4(1.5 g·cm-3),配制这种H2SO4 100 mL需要18.4 mol·L-1的浓H2SO4________ mL(保留一位小数)。
(2)加入氧化剂H2O2后,有Fe(OH)3沉淀出现,没有Cu(OH)2沉淀出现,若溶液中c(Fe3+)=2.6×10-18 mol·L-1,则溶液中c(Cu2+)的取值范围是________mol·L-1。(已知Ksp[Fe(OH)3]=2.6×10-39,
Ksp[Cu(OH)2]=2.2×10-20)
(3)加入NH4HCO3后生成的沉淀是形态均为Zna(OH)b(CO3)c(a、b、c为正整数)的两种碱式碳酸锌A和B的混合物,A中a=5、b=6,则生成碱式碳酸锌A的化学方程式为__________________________________________________。
(4)取洗涤、烘干后的碱式碳酸锌A和B的混合物49.70 g,其物质的量为0.10 mol,高温焙烧完全分解得到37.26 g ZnO、3.584 L CO2(标准状况下)和水,通过计算求出碱式碳酸锌B的化学式。
Prior to the UML, there was no clearleading (66) Ianguage. Users had to choose from among many similar modeling languages with minor differences in overall (67) power. Most of the modeling languages shared a set of commonly accepted concepts that are expressed slightly differently in various languages. This lack of (68) discouraged new users from entering the OO market and from doing OO modeling, without greatly expanding the power of modeling. Users longed for the industry to adopt one, or a very few, broadly supported modeling languages suitable for (69) usage.
Some Vendors were discouraged from entering the OO modeling area because of the need to support many similar, but slightly different, modeling languages. In particular, the supply of add-on tools has been depressed because small vendors cannot afford to support many different formats from many differem (70) modeling tools. It is important to the entire OO industry to encourage broadly based tools and vendors, as well as niche products that cater to the needs of specialized groups.
(69)处填()。
A.distincitive
B.special-purpose
C.separate
D.general-purpose