Number 18 is correct, number 19 is the particles speed up and the substance expands, and number 20 is decrease in volume
I’m pretty sure the answer is triclinic
C. Hot tea is capable of dissolving more sugar then iced tea
The full question can be seen below:

The decomposition of
is represented by the equation above.
A student monitored the decomposition of a 1.0 L sample of
at a constant temperature of 300K and recorded the concentration of
as function of time. The results are given in the table below:
Time (s) 
0 2.7
200 2.1
400 1.7
600 1.4
The
produced from the decomposition of the 1.0 L sample of
is collected in a previously evacuated 10.0 L flask at 300 K. What is the approximate pressure in the flask after 400 s?
(For estimation purpose, assume that 1.0 mole of gas in 1.0 L exerts a pressure of 24 atm at 300 K).
Answer:
1.2 atm
Explanation:
Considering all assumptions as stated above;

Initial 2.7 mole --- ---
Change -1.0 --- 
Equilibrium 1.7 mole --- 0.5 mole
To determine the concentration of O₂; we need to convert the moles to concentration for O₂ = 
= 
= 0.05 
Thus, based on the assumption that "1.0 mole of gas in 1.0 L exerts a pressure of 24 atm"
∴ 0.05
will give rise to = 0.05
× 24
= 1.2 atm