When it comes to physical changes like phase changes, there are two types of heat energy: sensible heat and latent heat. Sensible heat is the heat absorbed/released when you heat the substance but it doesn't change phase. An example would be heating lukewarm water. The substance is liquid all throughout. Latent heat, on the other hand, is the heat absorbed/released when there is a phase change. An example would be boiling water, because it changes liquid to vapor.
Hence, for freezing liquid, you use the latent heat, specifically the heat of fusion. The answer should be
2.5 g * (1 mol/18.02 g) * 6.03 kJ/mol = 0.84 kJ/mol
The answer is not in the choices. You only use Hvap if you boil water.
d = diameter of the seat = 12 inch
we know that , 1 inch = 0.0254 m
hence
d = diameter of the seat = 12 inch = 12 (0.0254) m = 0.305 m
r = radius of seat = diameter/2 = d/2 = 0.305/2 = 0.1525 m
A = area of seat = πr²
m = mass of the person = 65 kg
g = acceleration due to gravity = 9.8 m/s²
F = force due to weight of person on the seat = mg
pressure on the seat is given as
P = F/A
P = mg/A
P = mg/(πr² )
inserting the values
P = (65 x 9.8)/((3.14) (0.1525)²)
P = 8723.1 N/m²
12+70= 82 g
(12/82)x100 = 14.6%
The answer is given to one decimal place.
