问题 计算题

(8分)25℃时,将体积Va,pH=a的某一元强碱与体积为Vb,pH=b的某二元强酸混合。

(1)若所得溶液的pH=11,且a=13,b=2,则Va︰Vb=                         

(2)若所得溶液的pH=7,且已知Va>Vb,b=0.5a,b值可否等于4      (填“可”或“否”)

(3)为了更好的表示溶液的酸碱性,科学家提出了酸度(AG)的概念,AG的定义为AG=lg

25℃时,若溶液呈中性,则AG=                ,溶液的pH与AG的换算公式为AG=                          (要简化)。

答案

(1)  1: 9      (2) 可      (3)   0       -2pH+14

(1)混合后溶液pH为11,说明碱过量,则

(2)强酸强碱恰好中和则符合公式:

故b值可以等于4

(3)25℃时,若溶液呈中性,则c(H+)=c(OH),代入AG=lg=0

AG=lg=

完形填空

When I was 8 years old, I once decided to run away from home. With my suitcase packed and some sandwiches in a bag, I started for the front door and said to Mom, “I_____小题1:__ (leave).”

“If you want to run away , that’s all right,” she said. “But you came into this home __小题2:___ anything and you can leave the same way.” I threw my suitcase and sandwiches on the floor heavily and started for the door again.

“Wait a minute,” Mom said. “I want your _小题3:__ back. You didn’t wear anything when you arrived.” This really angered me. I tore my clothes off—shoes, socks, underwear and all—and   shouted , “Can I go now?” “Yes,” Mom answered, “but once you close that door, don’t expect ___小题4:___(come )back.”

I was so angry that I slammed (砰地关上) the door and stepped out on the front porch.   ___小题5:____ (sudden) I realized that I was outside, with nothing on. Then I noticed that down the street, two neighbor girls were walking toward our house. I ran to bide behind a big tree in our yard at once. After a while, I was sure the girls___小题6:___ (pass) by. I dashed to the front door and banged on it loudly.

“Who’s there?” I heard.

“It’s Billy! Let me in!”

The voice behind __小题7:___ door answered, “Billy doesn’t live here anymore. He ran away from home.” _____小题8:____ (glance) behind me to see if anyone else was coming, I begged, “Aw, c’mon, Mom! I’m still your son. Let me __小题9:___!”

The door inched open and Mom’s smiling face appeared. “Did you change your __小题10:___ (decide) about running away?” she asked.

“What’s for supper?” I answered. 

单项选择题