To calculate the atomic mass of a single atom of an element, add up the mass of protons and neutrons.
        
             
        
        
        
Answer:
P2 = 19.2atm
Explanation:
Initial pressure (P1) = 16atm
Initial temperature (T1) = 340K
Final temperature (T2) = 408K
Final pressure (P2) = ?
This question involves the use of pressure law
Pressure law states that the pressure of a fixed mass of gas is directly proportional to it's temperature provided that volume is kept constant. 
Mathematically, 
P = kT, k = P / T
Therefore, 
P1 / T1 = P2 / T2 = P3 / T3 = ......=Pn / Tn
P1 / T1 = P2 / T2
We need to solve for P2
P2 = (P1 × T2) / T1
Now we can plug in the values and solve for P2
P2 = (16 × 408) / 340
P2 = 6528 / 340
P2 = 19.2atm
The final pressure (P2) of the gas is 19.2atm
 
        
             
        
        
        
It's C, the amount of protons in the nucleus of each atom :)
        
             
        
        
        
Answer:
Place 20.0 g NaOH(s) in a flask and dilute to 1.00 L with water.
Explanation: