问题 选择题

不用其它试剂,欲将HCl、CaCl2、Na2CO3、AgNO3四种无色未知液鉴别开来,先任取其中一种试剂分别滴入另三种试剂中,根据现象可以得出的结论是(Ag2CO3为沉淀)(  )

A.只能将四种物质分为两组

B.四种物质中只有可能首先确定盐酸

C.可以确定滴入其它三种试剂中的试剂是哪种物质

D.A、B、C均不正确

答案

根据题目中提供的物质,可以发生的反应主要有:

(1)2HCl+Na2CO3=2NaCl+H2O+CO2↑,

(2)HCl+AgNO3=AgCl↓+HNO3

(3)Na2CO3+CaCl2=CaCO3↓+2NaCl,

(4)Na2CO3+2AgNO3=Ag2CO3↓+2NaNO3

(5)CaCl2+2AgNO3=2AgCl↓+Ca(NO32

(6)HCl溶液和CaCl2溶液混合不反应,无现象;

由以上分析可知:若取的是HCl,则发生的现象是:一个生成气体、一个生成沉淀、一个无现象;若取的是CaCl2,现象是:一个无现象、两个沉淀;若取的是Na2CO3,发生现象:一个生成气体、两个生成沉淀;若取的是AgNO3,则发生现象:三个沉淀;因此任取其中一种试剂分别滴入另三种试剂中,根据现象可以确定滴入其它三种试剂中的试剂是哪种物质;

故选C.

阅读理解

Alex Wood began fundraising when he was four years old. He sold lemonade and cookies to raise money for a school in Haiti. Later, Alex sent 15 bags of food he collected from his neighbors to a food store near his home which asked for donations(捐赠).

Alex wanted to help more people. He decided to donate to Heifer International, an organization that gives farm animals and farm training to poor people around the world. His goal: $5,000 for a “gift ark”. That amount would mean that 15 pairs of animals would be given to people in need. Those families would agree to give one of their animals’ young to other needy families.

Alex decided that baking was the best way to raise money. He started a business, named it Clean Hands Bakery, and now sells his baked goods year round. In his family’s kitchen, he created all kinds of cookies and cakes. He says his top sellers are lemon pound cakes and chocolate cupcakes. Alex likes the baking as much as the fundraising. “I like it that you can take so many ingredients(原料) that don’t taste good on their own and come up with something amazing,” he says.

In September 2011, Alex reached his goal of $5,000 and bought a gift ark. “I feel absolutely overjoyed that I got to my goal,” he says. “I can’t help everybody by myself, but I can do my part, which I hope will inspire other people to do their part, too.” One of the people Alex has already inspired is his younger brother. “He had people donate to me, instead of giving him a birthday present.” Alex explains. “In the end he donated $200 toward my goal.”

So now that he’s met his goal of a gift ark, will Alex keep baking and fundraising? He says yes. He wants to end world hunger, one cupcake at a time.

小题1:What did Alex Wood donate to Heifer International?

A.$5.000 in cash

B.Farm animals

C.A gift ark

D.Lemon Hands Bakery小题2: According to the passage, Clean Hands Bakery ______.

A.was set up in September 2011

B.uses many unusual ingredients

C.belongs to Heifer International

D.sells food cooked by Alex himself小题3: What’s Alex’ younger brother’s attitude towards his fundraising idea?

A.Doubtful

B.Curious

C.Supportive

D.Uncaring小题4: What would be the best title for the passage?

A.A charity helping the poor.

B.Feeding the world by baking.

C.The best way to raise money.

D.Cooking with different ingredients.

单项选择题