C1: dùng quỳ tím. Axit axetic làm quỳ hoá đỏ. Rượu etylic thì ko. 

C2: Lấy dư mỗi chất axit axetic và rượu etylic. Sau đó thả quỳ tím, nhỏ từ từ NaOH vào. Ống axit axetic thấy quỳ chuyển dần đỏ -> tím -> xanh. Ống rượu etylic chỉ có màu tím. 

2. 

IV. complete the sentences using the word in brackets so that it has a similar meaning to the first sentence.

1. Nam is taller than Hung (not) 

=> Hung is...................................................................

2. this computer is more expensive than I thought (as) 
=> this computer...........................................................
3. I have never read a better book than this one (ever)
=> this is the................................................................
4. Hoa is the tallest girl in the class (than)
=> every other girl in the class.....................................
5. mount everest is the highest mountain in the world ( higher)
=> no mountain in.........................................................
6. no one in the class runs as fast as Tim (runner)
=> Tim............................................................................