问题 问答题

将锌片和铜片用导线相连浸入稀硫酸中组成原电池,两电极间连接一个电流计,装置如图:

(1)锌片上发生的电极反应:______;铜片上发生的电极反应:______;

(2)若该电池中两电极的总质量为60g,工作一段时间后,取出锌片和铜片洗净干燥后称重,总质量为47g,试计算产生标准状况氢气的体积为多少L?(请写出计算过程)______.

答案

1)该原电池中,锌易失电子发生氧化反应而作负极,电极反应式为:Zn-2e-=Zn2+,铜作正极,正极上氢离子得电子发生还原反应,电极反应式为:2H++2e-=H2↑,

故答案为:Zn-2e-=Zn2+;2H++2e-=H2↑;

(2)负极上锌生成锌离子进入溶液而导致质量减少,正极上氢离子得电子生成氢气,所以正极质量不变,两个电极减少的质量是锌的质量,锌和稀硫酸反应离子方程式为2H++Zn=Zn2++H2↑,

根据锌和氢气之间的关系式得氢气的体积=

(60g-47g)
65g/mol
1
×1×22.4L/mol=4.48L,

故答案为:4.48L.

问答题 简答题
单项选择题

For many people today, reading is no longer relaxation. To keep up their work they must read letters, reports, trade publications, interoffice communications, not to mention newspapers and magazines: a never ending flood of words. In (1) a job or advancing in one, the ability to read and comprehend (2) can mean the difference between success and failure. Yet the unfortunate fact is that most of us are (3) readers. Most of us develop poor reading (4) at an early age, and never get over them. The main deficiency (5) in the actual stuff of language itself—words. Taken individually, words have (6) meaning until they are strung together into phrases, sentences and paragraphs. (7) , however, the untrained reader does not read groups of words. He laboriously reads one word at a time, often regressing to (8) words or passages. Regression, the tendency to look back over (9) you have just read, is a common bad habit in reading. Another habit which (10) down the speed of reading is vocalization—sounding each word either orally or mentally as (11) reads.

To overcome these bad habits, some reading clinics use a device called an (12) , which moves a bar(or curtain) down the page at a predetermined speed. The bar is set at a slightly faster rate (13) the reader finds comfortable, in order to "stretch" him. The accelerator forces the reader to read fast, (14) word by word reading, regression and subvocalization practically impossible. At first (15) is sacrificed for speed. But when you learn to read ideas and concepts, you will not only read faster, (16) your comprehension will improve. Many people have found (17) reading skill drastically improved after some training. (18) Charlie Au, a business manager, for instance. His reading rate was a reasonably good 172 words a minute(19) the training; now it is an excellent 1,378 words a minute. He is delighted that how he can (20) a lot more reading material in a short period of time.

第(16)空应选择()

A.but

B.nor

C.or

D.for