问题 选择题

室温时,在水电离出c(H+)=1.0×10-14mol·L-1的溶液中,一定能大量共存的离子组是

A.K+、Na+、HCO3-、Cl-

B.K+、MnO4-、Br-、Cl-

C.Na+、Cl-、NO3-、SO42-

D.Al3+、NH4+、Cl-、SO42-

答案

答案:C

水电离出c(H+)=1.0×10-14mol·L-1的溶液可能显酸性,也可能显碱性。

A 碳酸氢根离子既能跟酸反应,也能跟碱反应。

B 在酸性环境中,高锰酸根离子和溴离子不能共存

C 在酸性、碱性都能共存

D 在碱性环境不能共存

单项选择题
单项选择题

Can you believe it There’s a world paper shortage. There’s a national bottle shortage, and we’re running out of raw materials like timber and tin -- or so the papers say. Well, I’ve just emptied my shopping basket after my weekly shopping trip and it was full of things made from these scarce materials. Half of what I’d bought I threw away at once; all those unnecessary paper bags, plastic bags, fresh wrapping paper and old newspapers they put the food in nowadays.
Modern packaging makes shopping cleaner and more convenient, but at what cost Every time you throw away a paper bag you’re throwing away part of a tree -- and trees don’t grow overnight! At this rate there soon won’t be any trees left, and then what shall we do
Perhaps we’ll learn to do what my mother did. She used to keep a store of paper bags in a kitchen drawer and use them again and again for her shopping. Most goods were sold loose in those days. And the shopkeeper weighed out the amount you wanted. Of course, liquid goods have always been sold in bottles or cans, but why can’t we use these containers more than once If we re-use all our bottles we would save on the raw materials and energy needed to make new ones. At the moment 90% of our rubbish is just dumped. It’s time we started to think seriously about the growing shortage of raw materials in the world today.

What problem does the author find from the newspapers
[A] There’s paper shortage. [B] There’s timber shortage.
[C] There’s raw material shortage. [D] There’s tin shortage.