题干

某密闭容器中有X、氧气和二氧化碳三种物质,在一定条件下充分反应,测得反应前后各物质的质量如下表.根据表中信息,判断下列说法正确的是()


A:该反应为置换反应

B:X中一定含有碳、氢两种元素

C:表中“待测”值为5

D:反应生成的CO2和H2O的质量比为45:36

上一题 下一题 0.0难度 选择题 更新时间:2020-04-25 10:07:42

答案(点此获取答案解析)

B

同类题5

阅读理解

Walk For Charity

Dear Friend,

    Please join us for our annual Walk For Charity.Starting in Weldown,you and your friends can choose a delightful 10,20 or 30 kilometers' route.

    The money raised will provide support to help people all over the world.Start collecting your sponsors now and then simply come along on the day.Please read the instructions below carefully,especially if you require transport to and from Weldown.

    See you on Sunday 15 April.

    V Jessop: Walk coordinator

    PS.Well done to last year's walkers for helping to raise a grand total of £21,000.The money has already been used to build a children's playground.

    START TIME:

    30 km: 8-10 am      20 km: 8-10:30 am      10 km: 8-11:30 am

    The organizers reserve the right to refuse late-comers.

    CLOTHING should be suitable for the weather.If rain is forecast,bring some protection and be prepared for all possibilities.It is better to wear shoes that have been worn in,rather than ones that are new.

    ROUTE MAPS will be available from the registration point.The route will be sign-posted and arranged.Where the route runs along the road,walkers should keep to one side in single file,facing oncoming traffic at all times.If you need help along the route,please inform one of the staff.

    Free car parking is available in car parks and on streets in Weldown.

    BUSES:

    For the 10 and 20 kilometers' routes,a bus will be waiting at Fenton to take walkers back to Weldown.The bus will leave every half hour starting at midday.The service is free and there is no need to book.