有一种氯化钠与氯化钾的混合物，它所含钾与钠的物质的量之比为3_爱下问搜题

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问题填空题

有一种氯化钠与氯化钾的混合物，它所含钾与钠的物质的量之比为3∶1，求：

(1)混合物中氯化钾的质量分数。

(2)含1 mol Cl^－的混合物的质量。

答案

(1)79.3%(2)70.5 g

题目分析：（1）则设混合物中有1mol的氯化钠，则氯化钾有3mol，混合物的总质量=1*58.5+3*74.5=282g，所以氯化钾的质量分数=(74.5*3/282)*100%=79.3%

(2)总的氯离子为1mol，所以氯化钾为0.75mol,氯化钠为0.25mol,所以混合物的质量="0.75*74.5+0.25*58.5=70.5" g

点评：本题抓住在氯化钾中，氯离子的物质的量等于钾离子的物质的量等于氯化钾的物质的量，而且计算过程中需要对物质的量与质量间的换算非常熟练。

完形填空

I walked into the grocery store not particularly interested in buying something. The sorrow of   1 my husband of 37 years was still too painful. And this grocery store held so many sweet 2 . Bob often came with me and almost every time he'd 3 to go off and look for something special. I'd always see him walking down the walkway   4 the three yellow roses in his hands. Bob knew I loved yellow roses. With a heart   5  with pain, I came to the meat shelf, I searched for the 6  small steak and remembered how Bob had loved his steak.
Suddenly a woman came beside me. She was in a soft green dress. I   7 as she picked up a large pack of T-bones,   8 them in her basket, hesitated, and then put them back. She saw me watching her and she smiled. "My husband loves T-bones, but   9 , at these prices, I don't know."
"My husband passed away eight days ago," I told her. "Buy him the steaks. And value every   10 you have together."
She smiled and I saw the feeling in her   11  as she placed the package in her basket and   12  away. I turned and pushed my cart forward too. Several minutes later I saw first the green suit and then 13 the pretty lady coming to me. In her arms she carried something. On her face was the   14  smile I had ever seen.
As she came closer, I saw what she held and   15  welled down. "These are for you, " she said and placed three beautiful yellow roses in my arms. She placed a gentle kiss on my cheek, then smiled again. I wanted to tell her what the roses   16 , but still unable to speak. I watched as she walked away as tears clouded my   17 . I looked down at the beautiful roses and found it almost 18 . How did she know?
Suddenly the   19  seemed so clear. I wasn't alone. "Oh, Bob, you haven't   20  me, have you?" I whispered, with tears in my eyes. He was still with me, and she was his angel.

B．disappointed

单项选择题

从购买的角度看，以下哪一项是产业市场购买行为的特点（）

A.直接采购

B.购买者的非专业性

C.批量小

D.需求的弹性大