题干

为鉴别K2CO3和NaHCO3两种白色固体,有4位同学分别设计了下列四种不同方法,其中不可行的是

A:分别配成1mol/L的溶液,各取1mL滴加1滴酚酞试液,比较颜色深浅

B:分别取样在试管中加热,将可能产生的气体通入澄清石灰水,观察有无白色浑浊

C:分别取样配成溶液,滴加Ba(OH)2溶液,观察有无白色沉淀

D:分别配成溶液,滴加CaCl2溶液,观察有无白色沉淀

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答案(点此获取答案解析)

C

同类题3

阅读下列短文,从各题所给的四个选项(A B C D)中,选出最佳选项。

B

    Do you shop online with websites like Taobao? The money you pay doesn't go directly to the seller. Instead, it goes through Alipay, which keeps your money for a while. After you receive your goods and click the "confirm receipt" button, Alipay then gives the money to the seller.

    The process is called "third party online payment". There is a transfer station, or a third account, between sellers and buyers to make online shopping safe. Buyers don't need to worry about paying for goods and then receiving nothing. Sellers also get rid of the risk of receiving no money after sending out goods.

    These transfer stations are usually set up by payment service companies such as Alipay, Tenpay and Yeepay. Among them, Alipay is the biggest in China. It has more than 270 million active users, according to Xinhua.

    While most online sellers and shoppers like the third party online payment system, banks are not very happy. That is because companies like Alipay are fighting over money with the banks. Users can invest in financial products through Alipay and make money. Thus lots of people choose to put money in Alipay rather than in banks.

    But WeChat payment is not the same. WeChat doesn't have its own account. When paying through WeChat, the buyers' money goes directly to the sellers. That's why so many people are excited about receiving and handing out "red envelopes" or gift money to their friends on WeChat.

    Whether Alipay or WeChat payment, they are all trying to attract more users and make online shopping easier. These two companies are also promoting payments through fingerprints. New payment methods such as quick response codes have become popular too.