Bài 20:  Nguyên tố A có 2 đồng vị X và Y có số nguyên tử tỉ lệ với nhau là 27 7/23 . Hạt nhân đồng vị X chứa 35 proton và 44 nơtron. Hạt nhân đồng vị Y chứa nhiều hơn X 2 nơtron. Xác định nguyên tử khối trung bình và tên nguyên tố A

David Evans is a farmer. He does farming on his own land in Wales. The farm has (1).............. his family for generations. The soil is poor. David (2)................ sheep on his land. He does not employ (3)................ fulltime workers. His sons help him when they are not (4)........... school. His wife adds to the family income by (5) ............... eggs which her hens produce. In summer she often (6) ............... paying guests into the farmhouse. The guests from the city enjoy their quiet holiday in the clean country (7)............... and Mrs. Evans enjoys having some (8).............. money to spend on clothes for her children and herself. However, it is a lonely life for the Evans family when the guests have gone. The question is that if his children want to (9) ............... the farm when Mr. Evans gives up working. Country life is quiet and (10) ............... ​to them. It is quite likely that they will leave the farm for the city some day. 1.a. been to​b. belonged to​c. possessed​d. depended on 2.a. feeds​b. Grows​c. raises​d. leads 3.a. some​ b. more​c. much​d. any 4.a. in​b. for​c. at​d. on 5.a. selling​b. sells​c. to sell​d. sell 6.a. take​b. takes​c. took​d. is taking 7.a. wind​b. sights​c. life​d. air 8.a. more​b. free​c. extra​d. interest 9.a. take off​b. take over​c. take after​d. take care 10.a. interesting​b. exciting​c. dull​d. peaceful

B1: Hòa tan 8g hỗn hợp gồm kim loại A Có hóa trị 2 và kim loại B có hóa trị 3 phải dùng 340ml dung dịch HCL 2M Cô cạn dung dịch sau phản ứng thu được bao nhiêu gam muối khan

B2: Cho 8,8gam CO2 vào 400ml dd Ca(OH)2 1M.Muối tạo thành sau phản ứng là gì?

B1: Dung dịch KOH có thể phản ứng với tất cả các chất trong dãy nào sau đây A/ CO2, K2SO4 B/SO2 , Na CL C/CaCO3, H2SO4 D/HCL, Cu(NO3)2