Đáp án B
G ọ i n C 2 H 3 C O O H = x ( m o l ) ; n H C O O H = y ( m o l ) n C 2 H 3 C H O = z ( m o l ) . T a c ó h ệ p h ư ơ n g t r ì n h x + y + z = 0 , 04 72 x + 46 y + 56 z = 2 , 2 n N a O H = x + y = 0 , 03 ⇔ x = 0 , 01 y = 0 , 02 z = 0 , 03 V ậ y n B r 2 = n C 2 H 3 C O O H + n H C O O H + 2 n C 2 H 3 C H O = 0 , 05 ( m o l )
=> m=8(g)