Answer:
Explanation:
exothermic reactions are the reactions which involve the release of energy.
the energy released can be of any forms ,for example heat,light .
all the combustion reactions are exothermic reactions
 
        
             
        
        
        
Answer:
The answer to your question is: 2.20 x 10 ²³ molecules
Explanation:
Data
mass = 45.7 g
molecules of CF₂Cl₂ = ?
Process
1.- Calculate the mass number of CF₂Cl₂
    C = 12    F =2 x 19    Cl = 2 x 35.5
    total = 12 + 38 + 71
    total = 121 g
2.- Use the Avogradro's number to solve the problem
                        121 g -------------------  6.023 x 10²³ molecules of CF₂Cl₂
                         45.7 g ---------------     x
                         x = (45.7 x 6.023 x 10²³) / 121
                         x = 2.75 x 10²⁵ / 121
                         x = 2.20 x 10 ²³ molecules