Iron rusts when in contact with water.
        
             
        
        
        
The way you want to find the percent composition would be by breaking down the problem like so:
K= atomic mass of K which is 39.098
Mn = atomic mass of Mn which is 54.938
O= atomic mass of o which is 15.999
Then you want to add 39.098+ 54.938+ 15.999 and you get 110.035 which is the molar mass for KMnO 
Then you want to take each molar mass and then divide it 110.035 and multiply by 100 
Ex. K = 39.098/ 110.035 and the multiply what you get by a 100 
You do this for the other elements as well good luck!
        
             
        
        
        
Answer: 5.22×10^24ato^2 H2O
Explanation:
 
        
             
        
        
        
Answer:
25.45 Liters
Explanation:
Using Ideal Gas Law PV = nRT => V = nRT/P
V = (1mole)(0.08206Latm/molK)(298K)/(1atm) = 25.45 Liters