问题 填空题

碳酸钙常用作牙膏的摩擦剂。某同学设计了一种制备碳酸钙的方案,其流程图如下:(所用石灰石含有杂质SiO2

回答下列问题:

(1)充分煅烧110吨石灰石得到固体66吨。标准状况下生成二氧化碳的体积为______________L,石灰石中碳酸钙的质量分数为______________%。

(2)假设第①步反应完全进行,则第②步反应过滤后得到的不溶性滤渣的成分为________________________。

(3)第③步反应一般不采用通入CO2的主要原因是______________________,

相应的离子方程式为_____________________________________。

(4)CaCO3是一种难溶物质,25℃时其Ksp=2.8×10-9。现将等体积的CaCl2溶液与Na2CO3溶液混合,若Na2CO3溶液的浓度为2.0×10-4 mol/L,则生成沉淀所需CaCl2溶液的物质的量浓度最小是______________。

(5)某学生用石灰石为原料,设计了另一种制备碳酸钙的实验方案,其流程图如下:

与前一方案相比较,该方案的优点是_________________________________。

答案

(1)2.24×107 90.9

(2)CaSiO3

(3)通入CO2的量不易控制,使生成的碳酸钙在CO2过量的条件下溶解

CaCO3+CO2+H2O=Ca2+2HCO3-

(4)5.6×10-5 mol/L

(5)不需要加热,操作简单,减少来自燃料的污染

(1)根据质量差生成CO2 44吨,物质的量为1×106 mol,体积为2.24×107 L,对应CaCO3为100吨质量分数为90.9%。

(2)SiO2与生成的CaO反应生成CaSiO3

(3)通入CO2的量不易控制,使生成的碳酸钙在CO2过量的条件下溶解

CaCO3+CO2+H2O=Ca2+2HCO3-

(4)Ksp=2.8×10-9=[ Ca2][CO32-]=2.0×10-4×0.5×x×0.5,x=5.6×10-5 mol/L。

(5)不需要加热,操作简单,减少来自燃料的污染。

单项选择题
单项选择题

Millions of Americans and foreigners see GI.Joe as a mindless war toy, the symbol of American military adventurism, but that’ s not how it used to be. To the men and women who (1) in World War I1 and the people they liberated, the GI. was the (2) man grown into hero, the pool farm kid torn away from his home, the guy who (3) all the burdens of battle, who slept in cold foxholes, who went without the (4) of 1hod and shelter, who stuck it out and drove back the Nazi reign of murder. This was not a vohmteer soldier, not someone well paid, (5) an average guy, up (6) the best trained, best equipped, fiercest, most brutal enemies seen in centuries.

His name is not much. GI. is just a military abbreviation (7) Govermnent Issue, and it was on all of the article (8) to soldiers. And Joe A common name for a guy who never (9) it to the top. Joe Blow, Joe Magrae... a working class name.The United States has (10) had a president or vieepresident or secretary of state Joe.

GI. Joe had a (11) career fighting Geman, Japanese, and Korean troops. He appears as a character, or a (12) of American personalities, in the 1945 movie The Story of GL Joe, based on the last days of war correspondent Ernie Pyle. Some of the soldiers Pyle (13) portrayde themselves in the fihn. Pyle was famous for covering the (14) side of the warl, writing about the dirt-snow-and-mud soldiers, not how many miles were (15) or what towns were captured or liberated. His reports (16) the "willie" cartoons of famed Stars and Stripes artist Bill Maulden. Both men (17) the dirt and exhaustion of war, the (18) of civilization that the soldiers shared with each other and the civilians: coffee, tobacco, whiskey, shelter, sleep. (19) Egypt, France, and a dozen more countries, G. I. Joe was any American soldier, (20) the most important person in their lives.

17()

A.neglected

B.avoided

C.emphasized

D.admired