Câu 1: Trình bày phương pháp hóa học nhận biết a. 3 dung dịch: HCl , Na2SO4 , NaCl.
b. 3 dung dịch:NaOH , NA2CO3 , NaCl.
c. 4 dung dịch:HCl , H2SO4 , NaCl , Na2SO4.
Viết phương trình phản ứng xảy ra (nếu có)

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