65. Hòa tan hết m gam FeS trong lượng dư dung dịch HNO3 đặc, sau đó thêm BaCl2 dư được 23,3 gam kết tủa. Giá trị của m: A. 12,0. B. 8,8. C. 18,6, D. 24,0. 66. Hoà tan 13,5 gam một kim loại chưa rõ hoá trị vào dung dịch HNO3 dư thu được 3,36 lít khí N2 duy nhất (đktc). Kim loại đó là A. Zn. B. Al. C. Mg. D. Fe. 67. Hoà tan hoàn toàn 19,5 gam một lim loại X có hoá trị cao nhất là 2 vào dung dịch axit nitric dư thu được 4,48 lít khí (đktc) không màu và hoá nâu trong không khí. X là A. Zn. B. Mg. C. Cu. D. Ba.

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