(12分) 白云石(主要成分为CaCO4,MgCO2)可用作碱性耐火材料和高炉

题型:填空题

问题:

(12分)

 
白云石(主要成分为CaCO4,MgCO2)可用作碱性耐火材料和高炉炼铁的溶制等。

  (1)甲同学利用加热法测定白云石中MgCO2的含量,

实验曲线如右图(MgCO4的分解温度比CaCO2

低)

①700℃(即B点)对剩余固体的主要成分为

        (填化学式)。

②该白云石中MgCO3的质量分数为         

(保留3位有效数字)。

(2)乙同学利用滴定法测定白云石中MgCO3的含量。已知:①滴定时,EDTA分别有Ca2+或Mg2+以物质的量之比1:1进行反应,可用K—B指示剂作为该滴定反应的指示剂;②实验条件下。Mg2+开始沉淀时的pH为10,沉淀完全时的pH为11.2,Ca2+开始沉淀时的pH为12。

步骤1:准确称取白云石试样m g,在烧杯中用适量稀盐酸完全溶解;

步骤2:冷却后全部转移到250mL容量瓶中定容,

步骤3:从容量瓶中移取试液25.00mL,用NaOH溶液调节溶液pH约为9.5;

步骤4:加入2滴K—B指示剂,以c mol/L的EDTA标准溶液滴定至终点,消耗EDTA溶液V1mL;

步骤5:再从容量瓶中移取试液25.00mL,         

步骤6:加入2滴K—B指示剂,继续以c mol/L的EDTA标准溶液滴定至终点,消耗EDTA溶液V2mL。

①根据上述分析数据,测得该白云石试样中MgCO3的质量分数为    (用含字母的代数式表示)。

②配制100mL c mol/L EDTA标准溶液,需要用到的玻璃仪器有烧杯、玻璃棒、量筒,

            

考点:化学科学探究
题型:填空题

计算题:一只220V、100W的白炽灯泡,在正常使用时,灯丝电阻和电流各是多少?

题型:填空题

易并发DIC的白血病类型是()

A.AML-M1

B.AML-M2

C.AML-M3

D.AML-M5

E.B-ALL

题型:填空题

To get a better night's sleep, get into bed with Zeo Introducing the revolutionary Zeo Personal Sleep Coach

The inability to get a good night's sleep is one of the top health issues. A night of poor sleep can affect one's mood, energy level, and performance. Most people have felt powerless to do anything about it -- until now. Introduing Zeo, a revolutionary approach to the problem of poor sleep.

A revolution in the science of sleep

Designed by leading sleep scientists,the Zeo Personal Sleep Coach is the first consumer product to help you take control of your sleep.Because understanding your sleep is the first step toward mananging it.

Wear the light Zeo Headband to bed and Zeo technology tracks and records your personal sleep patterns and wrielessly send them to the Zeo Bedside Display. When you wake up, you simply touch a button to get your sleep data: the time you took to fall asleep, your time in deep sleep and light sleep, and how often you woke up. Seeing how you slept is just the beginning. What you do with that information is what makes Zeo so remarkable.

Take control of your sleep

Zeo puts the science of sleep at your fingertips. The Zeo Bedside Display stroes your sleep data so you can easily upload it to the Zeo Peasonal Coaching website. Here you 'll find a collection of online tools that help you analyze you sleep and uncover the links between how you live and how your sleep. Zeo's Seven Step Sleep Fintness program assists you in creating a personalized action plan based on your own sleep pattems and goals, and delivers user-tailored coaching emails that help you get the sleep you need.

Try Zeo risk free,and enjoy free shipping

Order Zeo today and receive the headband, bedside display, full access to our powerful user website and you personalized, multi-week sleep coaching program--plus our satisfaction guarantee and free shipping.

ze?

The more you know, the better you sleep.

30-DAY money- back guarantee FREE SHIPPING

Call NOW to order. Call 888-794-9349

Zeo Personal Sleep Coach is neither a medical device nor a medical program and is notintended for the treatment of sleep disorders.

小题1:Zeo is a revolution in the science of sleep mainly because it _____.

A.can record one’s sleep process

B.is the first product to manage one’s sleep

C.is free of medical risks

D.provides access to sleep fitness websites小题2:What is the most remarkable feature of Zeo?

A.Its direct contact with sleep scientists.

B.Its individualized coaching program.

C.Its effectiveness in curing sleep disorders.

D.Its immediate analysis of sleep data.小题3:What customer service does Zeo provide?

A.Cheap online tools.

B.A 30-day action plan.

C.Personalized bedside display.

D.Free delivery of the product.小题4:The passage is primarily written to _____.

A.encourage people to try the new product

B.instruct people how to use a new tool

C.provide the latest health information

D.illustrate the importance of good sleep habit

题型:填空题

关于社区健康教育与健康促进概念的表述,不正确的是().

A.是有组织、有计划、有评价的活动与过程

B.以社区居民为对象

C.以促进社区健康为目标

D.以社区医疗机构为单位

E.适用于社区急、慢性疾病的综合防治

题型:填空题

君威中控面板以()度仰角设计,但按键过多不易操作。

A.20

B.22

C.27

D.30

更多题库