Answer:
m = 6.4 kg
Step-by-step explanation:
Now, we use the following equation to find the mass of the gel:

where,
P = (60 mm of Hg)(133.3 Pa/1 mm of Hg) = 7999.2 Pa = 7.99 KPa
ρ = density of gel =

m = mass of gel = ?
r = radius of cylindrical tank = 5 cm = 0.05 m
h = height of tank
Therefore,

m = 6.4 kg