Answer:
Since moles are just "some number of particles", and since one O2 molecule contains enough oxygen for two H2O molecules, you need 2.5 moles of O2 for 5 moles of H2O.
 
        
             
        
        
        
The hydrogen bonds that form between water molecules account for some of the essential and unique properties of water. The attraction created by hydrogen bonds keepswater liquid over a wider range of temperature than is found for any other molecule its size.
Hope this helped!
        
             
        
        
        
Answer:
3 moles
Explanation:
SrCO3 
Mass = 442.8g
Molar mass = (87.6 + 12 * [16*3]) = 147.6g/mol
Number of moles = mass / molar mass
Number of moles = 442.8 / 147.6
Number of moles = 3
 
        
             
        
        
        
For the first one it’s 69 just count the little lines from the side.