Increasing order of strength needed to break bonds: 
temporary dipole induced dipole interactions 
Permanent dipole induced dipole interactions 
Hydrogen bonding
        
             
        
        
        
Answer:
Explanation:
The usefulness of a buffer is its ability to resist changes in pH when small quantities of base or acid are added to it. This ability is the consequence of having both the conjugate base and the weak acid present in solution which will consume the added base or acid.  
This capacity is lost if the ratio of the concentration of conjugate base to the concentration of weak acid differ by an order of magnitude. Since  buffers having ratios differing by more will have their pH driven by either the weak acid or its conjugate base . 
From the Henderson-Hasselbach equation we have that
pH = pKa + log [A⁻]/[HA]
thus
0.1 ≤  [A⁻]/[HA] ≤ 10
Therefore the log of this range is -1 to 1, and the pH will have a useful range of within +/- 1 the pKa of the buffer.
Now we are equipped to answer our question:
pH range = 3.9 +/- 1 = 2.9 through 4.9
 
        
             
        
        
        
Answer:
Mole fraction H₂ = 0.29
Partial pressure of H₂ → 88.5 kPa
Explanation:
You need to know this relation to solve this:
Moles of a gas / Total moles = Partial pressure of the gas / Total pressure
Total moles = 3 mol + 7.3 mol → 10.3 moles
Mole fraction H₂ → 3 moles / 10.3 moles = 0.29
Mole fraction = Partial pressure of the gas / Total pressure
0.29 . 304 kPa = Partial pressure of H₂ → 88.5 kPa
 
 
        
             
        
        
        
Answer:
Elements only contain one type of atoms while compounds contain two or more types of atoms.
Explanation:
An example of an element is sodium --> Na (only Na atoms)
An example of a compound can be water --> H2O (contain H and O atoms)
*But the particles within a compound are all the same.