A sample of Ascorbic acid (vitamin C) is synthesized in the laboratory; it contains 1.50 g of Carbon and 2.00 g Oxygen. Another sample of Ascorbic acid isolated from citrus fruits contains 6.35 g of Carbon. How many grams of Oxygen toes it contain ? Which law do you assume in answering this question ? 

1) 7.25 : Law of conservation of mass 

2) 6.35 : Law of definite proportions 

3) 8.47 : Law of definite proportions 

4) 6.35 : Law of multiple proportions

A radioactive element has half life period 1600 years. After 6,400 years, what amount will remain? 

(A) 1/2 

(B) 1/16 

(C) 1/8 

(D) 1/4