Ok, so... 20.219 grams is the mass of the flask with the water in it. 
10.267 grams is the mass of only the flask. Subtract them to find the water mass. 
20.219 g (flask+water) - 10.267 g (flask) = 9.952 g (water)
        
             
        
        
        
Answer:
It helps get you to the proof of the matter
Explanation:
 
        
             
        
        
        
Question 5) 
1 Hour: 100g
40 Minutes: 50g
20 Minutes: 25g
0 Minutes: 12.5g
Question 6)
160 Days: 80ou
120 Days: 40ou
80 Days: 20ou
40 Days: 10ou
0 Days: 5ou
Every period of time, the radioactive isotopes halve in numbers as they emit radiation. 
I think you now know the gist. Try doing the rest yourself. 
Good luck.
        
             
        
        
        
Answer:
1st one is right..it helps filter waste inside the cell.
 
        
             
        
        
        
Correct Answer: option 1 i.e. C
Reason: 
The the compound of interest i.e.  XCl4, since there are 4 Cl atoms bonded to X. This signifies that the valency of X is 4.
There atomic number of C is 6. It's electronic configuration is giving by 1s2 2s2 2p2. Thus, there are 4 electrons in valence shell of C. This signifies that valency of C is 4. Hence the compound present in present case is CCl4.