Answer:
frequency it the measure of the wave length. The measure of the peaks and troughs is how you measure the frequency. the distance between these is the wave length. 
 
        
             
        
        
        
$14.00
fee for a Law and rule book
 
        
             
        
        
        
Answer:
 9.29 mol
Explanation:
Given data:
Number of moles = ?
Mass = 148.6 g
Solution:
Number of moles = mass/ molar mass
Molar mass of CH₄ = 16 g/mol
Now we will put the values in formula.
Number of moles = 148.6 g/ 16 g/mol
Number of moles = 9.29 mol
Thus 148.6 g have 9.29 moles.
 
        
             
        
        
        
it only happensonce every 7 years