1) Cho một dung dịch chứa 4,12 gam muối NaX tác dụng với một lượng dư dung dịch AgNO3 dư thu được 7,52 gam kết tủa. a. Tính nguyên tử khối và gọi tên X. b. X có 2 đồng vị, phần trăm các đồng vị bằng nhau, đồng vị II có số nơtron nhiều hơn đồng vị I là 2 hạt. Tính số khối mỗi đồng vị.

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help me!Pleaseeeee I. Complete the second sentence so that it means the same as the sentence before. 1. Global warming has caused many natural disasters. Many natural disasters__________________________________________________ 2. After she had explained everything clearly, we started our work. Before we_____________________________________________________________ 3. I can’t come because I have to help my dad with something. If I_____________________________________________________________________ 4. Although he took a taxi, he still arrived late for school. In spite of______________________________________________________________ 5. “I am going to join the Science Club.”, said Nam Nam said_______________________________________________________________ II. Rearrange the words/phrases to make complete sentences. 1. had / better / rubbish / on / We / streets. / not / throw / the _______________________________________________________________________ 2. Our car / by / a mechanic / will / tomorrow morning. / be / serviced _______________________________________________________________________ 3. been / ever / an / you / English / Have / speaking / to/ country? _______________________________________________________________________ 4. lots / grammatical mistakes / in / I / my / writing. / made /of _______________________________________________________________________ 5. was / a / There / lastnight. / in / typhoon / Nam Dinh province _______________________________________________________________________ III. Make sentences using the words and phrases given. 1. They / asked / whether / there / be /water / Mars. _______________________________________________________________________ 2. What / happen / if / we / not / save / natural resources? _______________________________________________________________________ 3. Thanks to / progress / science and technology, / human life /change / better and better / recently. _______________________________________________________________________ 4. New York / be / biggest / city / the USA, / but / not / the capital. _______________________________________________________________________ 5. Noise pollution / big cities / can / lead / hearing / problems. _______________________________________________________________________