Independent Variable: a variable that you can change in an experiment
Dependent Variable: something that changes as you change the independent variable
control variable: something that is not changed throughout the experiment
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
To the top. Common knowledge my dude. Heat always rises to the top.
Transparency (also called pellucidity or diaphaneity) in the field of optics is the physical property of allowing light to pass through the material without significant light dispersion.