问题 问答题

将氯化镁和氯化钠的固体混合物25g,加入密度为1.2g/cm3、溶质的质量分数为20%的氢氧化钠溶液50mL,充分反应后,过滤;所得滤液显碱性,在此碱性滤液中加入73g溶质的质量分数为5%的盐酸,恰好完全反应.求恰好完全反应时,滤液的溶质质量分数.

答案

50mL氢氧化钠溶液中NaOH的质量为:50mL×1.2g/cm3×20%=12g;盐酸中HCl的质量为:73g×5%=3.65g(1分)

设与盐酸反应的NaOH的质量为x,生成的氯化钠质量为m1;与NaOH反应的氯化镁的质量为y,生成的氢氧化镁沉淀质量为z,生成的氯化钠质量为m2

NaOH+HCl═NaCl+H2O

40   36.5  58.5

x    3.65g  m1

40:x=36.5:3.65g

解之得x=4g(1分)

58.5:m1=36.5:3.65g

解之得 m1=5.85g

与氯化镁反应的NaOH的质量为:12g-4g=8g

MgCl2+2NaOH═Mg(OH)2↓+2NaCl

95     80     58         117

y      8g     z           m2

95:y=80:8g

解得y=9.5g

58:z=80:8g

解得z=5.8g

117:m2=80:8g

解得 m2=11.7g

则原混合物中氯化钠的质量为25g-9.5g=15.5g

最后得到的溶液中的氯化钠的质量为15.5g+5.85g+11.7g=33.05g

滤液的溶质质量分数为

33.05g
60g+73g+25g-5.8g
×100%≈21.7%

答:恰好完全反应时,滤液的溶质质量分数为:21.7%.

完形填空
On last Christmas Day, our parents’ home was full of joys of a close family relationship but this year things are     . Our father had gone on November 26, and this was our        Christmas without him. Mother was doing her best to be good, but I could tell this was especially       for her. I’m not sure       I should give her my planned Christmas gift.
A few months earlier I had painted two pictures of my parents. I’d planned to give them as       gifts.
While painting one day, I was surprised by the doorbell ringing. I opened the      . My father came. I showed       the paintings. Finally, with tears running down his face, he said, “I don’t believe it. Look, how beautiful your mother is. Will you let me decorate them with frames(边框)?” I       offered to send them to the frame shop the next day.
Several        had passed after my dad died. It seemed all        was taken away from my mother and me. I finally remembered to call about the paintings and was glad that my father had got a chance to see the pictures       he died. I was surprised when the shopkeeper told me my father had visited the shop,        the frames and had them wrapped.
As I        my mother’s sad eyes and unsmiling face, I        to give her Daddy’s and my gift.
After looking at the paintings and the card, with tear-filled eyes and a wide smile, she said, “ I knew Daddy would be     us on Christmas Day!”
I looked at the gift card with my father’s handwriting. “ Mother: Our daughter reminded me why I am so lucky. I’ll be looking at you always. Daddy.”  
小题1:
A.usual B.sameC.differentD.beautiful
小题2:
A.firstB.secondC.thirdD.last
小题3:
A.interesting B.hard C.easy D.proud
小题4:
A.whyB.if C.because D.so
小题5:
A.Mother’s Day B.birthday C.New Year D.Christmas
小题6:
A.door B.window C.boxD.present
小题7:
A.itB.herC.them D.him
小题8:
A.happilyB.sadly C.surpriselyD.loudly
小题9:
A.minutesB.hoursC.weeksD.years
小题10:
A.characterB.luck C.adviceD.happiness
小题11:
A.afterB.untilC.beforeD.when
小题12:
A.heard ofB.paid forC.shouted atD.gave up
小题13:
A.looked at B.looked after C.looked for D.looked around
小题14:
A.happenedB.forgotC.promisedD.decided
小题15:
A.forB.withC.onD.at
单项选择题