题干

下列解释事实的化学方程式或离子方程式错误的是(     )

A:向海带灰浸出液中加入硫酸、双氧水:2I-+2H++H2O2=I2+2H2O

B:自然界各种原生铜的硫化物经氧化、淋滤作用后产生的硫酸铜,遇到难溶液的PbS,慢慢转变为铜蓝(CuS):Cu2++SO42-+PbS═CuS+PbSO4

C:在燃煤时加入适量石灰石,可减少SO2的排放:2CaCO3+O2+2SO2═2CaSO3+2CO2

D:在盐碱地(含较多NaCl、Na2CO3)上通过施加适量CaSO4,可降低土壤的碱性:CaSO4+Na2CO3═CaCO3↓+Na2SO4

上一题 下一题 0.0难度 选择题 更新时间:2018-01-09 09:02:01

答案(点此获取答案解析)

C

同类题2

任务型阅读

    Reasons Why Physical Education is Important in School

    Are you looking for information about the importance of physical education in schools and why it should be emphasized? Do you want a healthy active lifestyle for your kids? Then this article can help you convince your kids that exercising and participation especially in school PE classes are important.

     It's a link to good health.

     ____ It's only in physical education classrooms that students learn the value of taking care of themselves through proper healthy eating and regular exercise.

    It's preventive measure against diseases.

    ____ Without any forms of diet management and control with the numerous processed foods students intake every day, a student's health can easily be at risk of many diseases. Physical education in schools is a preventive measure to teach students the value of regular exercise.

    ____

    Physical health allows students to function even better in classrooms. A good cardiovascular(心血管的) system developing from regular exercise promotes excellent blood and oxygen circulation. This means more nutrients circulate throughout the body which includes the brain. This circulation produces longer attention time during classes allowing longer concentration and better absorption.

     It builds self-esteem

    Students who are active in physical activities like basketball, volleyball and running are more confident with themselves according to most social school studies.____ In school, the physical education program introduces these sport activities to students allowing them to make choices of which sport areas they want to get involved in.

    ____

    Most physical education programs are holistic. The program allows students to interact together to a common goal, that is, to win and excel physically. It not only brings out the competitive sides of students working with both body and mind but also promotes sportsmanship.

    It promotes a physically active lifestyle.

    The purpose of physical education is to instill(逐渐灌输) in students, at an early age, the value of self-preservation and choosing a lifestyle that is good for both the mind and body.

A. Physical education plays a vital role in students' development and growth.

B. It's a program for muscle strength and fitness.

C. It's probably because of the dedication made to a sport that brings out the best in students.

D. It develops cooperation, teamwork and sportsmanship.

E. The value of physical fitness cannot be overstated too much.

F. It promotes academic learning.

G. Many doctors today agree that obesity is a serious health risk.