<u>Answer:</u>
<em>The amount of energy needed when water at 72 degrees c freezes completely at 0 degrees c is
Joules</em>
<em></em>
<u>Explanation:</u>

where
= Final T - Initial T

=30125J
Q is the heat energy in Joules
c is the specific heat capacity (for water 1.0 cal/(g℃)) or 4.184 J/(g℃)
m is the mass of water
mass of water is assumed as 100 g (since not mentioned)
is the heat energy required for the phase change
=mass × heat of fusion

Total heat =
Total Heat = 30123J + 33600J
= 63725 J
=
Joules is the answer
According to
Graham's Law of Diffusion," Diffusion of Gas is inversely proportional to square root of its Molecular Mass or Density".
rᵇ/rᵃ =

Or,
rᵇ/rᵃ =

----- (1)
As,
Ma = 275 g/mol
Mb = 205 g/mol
Putting Values in eq.1,
rᵇ/rᵃ =

rᵇ/rᵃ = 1.15
Result: Perfume B will diffuse 1.15 times faster than
Perfume A. Hence, Perfume B will be first smelled by the person.
Answer:
See explanation
Explanation:
TLC is a chromatographic method in which the solute is spotted on a plate and the plate is placed in an air tight chamber containing a solvent. The solvent is maintained below the level of the spot. The capillary movement of the solvent through the plate achieves the required separation.
If two spots have Rf values of 0.25 and 0.26 respectively and then the plate was removed from the developing chamber, subsequently, the residual solvent was allowed to evaporate from the plate, and then the plate was returned to the developing chamber.
It will be observed after the second development is complete that the new Rf values will be 0.50 and 0.52 respectively. It will just be as though the second chromatogram picked up from where the first chromatogram stopped.
Answer:
= 913.84 mL
Explanation:
Using the combined gas laws
P1V1/T1 = P2V2/T2
At standard temperature and pressure. the pressure is 10 kPa, while the temperature is 273 K.
V1 = 80.0 mL
P1 = 109 kPa
T1 = -12.5 + 273 = 260.5 K
P2 = 10 kPa
V2 = ?
T2 = 273 K
Therefore;
V2 = P1V1T2/P2T1
= (109 kPa × 80 mL × 273 K)/(10 kPa× 260.5 K)
<u>= 913.84 mL</u>