Answer : The pressure in the flask after reaction complete is, 2.4 atm
Explanation :
To calculate the pressure in the flask after reaction is complete we are using ideal gas equation.

where,
P = final pressure in the flask = ?
R = gas constant = 0.0821 L.atm/mol.K
T = temperature = 
V = volume = 4.0 L
= moles of
= 0.20 mol
= moles of
= 0.20 mol
Now put all the given values in the above expression, we get:


Thus, the pressure in the flask after reaction complete is, 2.4 atm
Since there are no given items, I will give a general answer. Energy....or the lack of it. Examples: Heat, electricity, force (when an item is moving and it impacts something, it heats up...friction is an example of this), etc
The mean radius of the sun is 432,450 miles (696,000 kilometers), which makes its diameter about 864,938 miles (1.392 million km). You could line up 109 Earths across the face of the sun. The sun's circumference is about 2,713,406 miles (4,366,813 km). The total volume of the sun is 1.4 x 1027 cubic meters.