问题 选择题

下列反应中属于分解反应的是(  )

A.硫在氧气中燃烧

B.加热分解高锰酸钾

C.从食盐水中得到食盐和水

D.铁丝燃烧

答案

A、硫、氧气两种物质反应生成一种物质二氧化硫,属于“多变一”的化合反应.故A错误;

B、一种物质高锰酸钾生成锰酸钾、二氧化锰、氧气三种物质,符合“一变多”的分解反应特点,故B正确;

C、从食盐水中得到食盐和水是物理变化,故C错误;

D、铁丝、氧气两种物质反应生成一种物质四氧化三铁,属于“多变一”的化合反应.故D错误.

故选B.

单项选择题
单项选择题

Vienna was one of the music centers of Europe during the classical period, and Haydn, Mozart, and Beethoven were all active there. As the (1) of the Holy Roman Empire (which included parts of present-day Austria, Germany, Italy, Hungary, Czech and Slovakia), it was a (2) cultural and commercial center (3) a cosmopolitan character. Its population of almost 250,000 (in 1800) made Vienna the fourth largest city in Europe. All three (4) masters were born elsewhere, but they were (5) to Vienna to study and to seek (6) . In Vienna, Haydn and Mozart became close friends and influenced each other’s musical (7) . Beethoven traveled to Vienna at sixteen to play for Mozart; at twenty-two, he returned to study with Haydn.

Aristocrats from all over the Empire spent the winter in Vienna, sometimes bringing their private (8) . Music was an important part of court life, and a good orchestra was a (9) of prestige. Many of the nobility were excellent musicians.

Much music was heard in (10) concerts where aristocrats and wealthy commoners played (11) professional musicians. Mozart and Beethoven often earned money by performing in these intimate concerts. The nobility (12) hired servants who could (13) as musicians. An advertisement in the Vienna Gazette of 1789 (14) : " Wanted, for a house of the gentry, a manservant who knows how to play the violin well. "

In Vienna there was also (15) music, light and popular in (16) . Small street bands of wind and string players played at garden parties or under the windows of people (17) to throw (18) money. Haydn and Mozart wrote many outdoor entertainment (19) , (20) they called divertimentos or serenades. Vienna’s great love of music and its enthusiastic demand for new works made it the chosen city of Haydn, Mozart and Beethoven.

11()

A.along

B.alongside

C.among

D.between