搜题请搜索小程序“爱下问搜题”
问题 选择题

能正确表示下列反应的离子方程式的是(    )

A．浓烧碱溶液中加入铝片：Al＋2OH-=AlO2-＋ H2↑

B．少量钠投入CuSO4溶液中：2Na＋Cu2+＋2H2O=2 Na+＋Cu(OH)2↓＋H2↑

C．碳酸钙与盐酸反应：CO32-＋2H+= H2O＋CO2↑

D．稀硫酸中加入铁粉：2Fe＋6H+=2Fe3+＋3H2↑

答案

答案：B

题目分析：铝与氢氧化钠溶液反应有水参加，所以A错误；金属钠投入到水溶液中与水反应生成氢氧化钠和氢气，然后NaOH再与CuSO4 反应生成Cu(OH)2 沉淀，所以B正确；碳酸钙是难溶固体不可拆，C错误；金属铁与稀硫酸反应生成二价铁，D错误；故选B。

问答题

OOO Festival organised a day of traditional folk music to take place on a public holiday. It entered into a contract with a popular folk music group to play at the festival as the main attraction. As the group was in p demand, OOO Festival paid 50% of the group’s fee in advance to secure the booking. It entered into a further contract with OOO Sweep to remove litter and clean the venue after the event had fi nished.One day before the event, the folk music group contacted OOO Festival to inform it that the group’s most important musician had been taken ill suddenly, but a replacement group had been engaged to take the group’s place.Due to an administrative error, OOO Sweep found that they had insuffi cient workers to perform the cleaning duties after the event, but hired another cleaning company to carry out this work.Required:

(b) Explain whether OOO Festival can claim a refund of the 50% deposit paid to the group that was unable to perform due to the illness of the musician. (3 marks)
查看答案
单项选择题

岗位操作人员必须按时进行（），及时掌握设备的润滑、泄漏、运行状态及工艺运行参数等。

A.日常点检

B.交接班

C.擦拭设备
查看答案