问题 实验题

小刚设计实验探究铁、铜、银三种金属的活动性顺序并分析相关问题。请填空:

(1)他设计的四种实验方案,所需试剂如下:

①铜、银、硫酸亚铁溶液 ②铁、银、硫酸铜溶液 ③银、硫酸亚铁溶液、硫酸铜溶液 ④铜、硫酸亚铁溶液,硝酸银溶液上述方案中,正确的是_______(填写序号)。

(2)某化工厂生产过程中的残液含有硝酸银和硝酸铜两种物质。小刚取少量该残液,分别盛在A、B两支试管中,再分别加入不同质量的铁粉,充分反应后过滤,分别取滤渣或滤液进行下表所示实验:

答案

(1)②④

(2)Fe(NO3)2;Ag

单项选择题
单项选择题

The history of English is conventionally, if perhaps too neatly, divided into three periods usually called old (or Anglo-Saxon) English, Middle English, and Modern English. The earliest period begins with the migration of certain Germanic tribes from the continent to Britain in the fifth century A. D, though no records of their language survive from before the seventh century, and it continues until the end of the seventh century or a bit later. By that time, Latin, Old Norse (the language of the Viking invaders), and especially the Anglo-Norman French of the dominant class after the Norman Conquest in 1066 had begun to have a substantial impact on the vocabulary, and the well-developed inflectional system that typifies the grammar of Old English had begun to break down.

The period of Middle English extends roughly form the twelfth century through the fifteenth. The influence of French (and Latin, often by way of French) upon the vocabulary continued throughout the period, the loss of some inflections and the reduction of others accelerated, and many changes took place within the grammatical systems of the language. A typical prose passage, specially one from the later part of the period, will not have such a foreign look to us as the prose of Old English, but it will not be mistaken for contemporary writing either.

The period of Modern English extends from the sixteenth century to our own day. The early part of this period saw the completion of a revolution in vowel distribution that had begun in late Middle English and that effectively brought the language to something resembling its present pattern. Other important early developments include the stabilizing effect on spelling of the printing press and the beginning of the direct influence of Latin, and to a lesser extent, Greek on the vocabulary. Later, as English came into contact with other cultures around the world and distinctive dialects of English developed in the many areas which Britain had colonized, numerous other languages made small but interesting contributions to our word-stock.

What is the most remarkable characteristic of Modern English()

A. Numerous additions to its vocabulary

B. Completion of a revolution in vowel distribution

C. Gradual changes in its grammatical system

D. The direct influence of Latin