The forensic technician at a crime scene has just prepared a luminol stock solution by adding 10.0 g of luminol into a total volume of 75.0 mL of H2O . What is the molarity of the stock solution of luminol

0.753M

Explanation:

Molecular formula of luminol is as follows: C8H7N3O2

Molecular formula of the luminol (C8H7N3O2) = 12(8) + 1(7) + 14(3) + 16(2)

= 96 + 7 + 42 + 32

= 177g/mol

mole of luminol = mass/molar mass

mole = 10 ÷ 177

mole = 0.0565 mol

Molarity can be calculated using the formula: Molarity = mol/volume (L)

Volume of water = 75.0 mL = 75/1000

= 0.075L

Molarity (M) = 0.0565 ÷ 0.075

The molarity of the stock solution = 0.753M

See explanation

Explanation:

We must recall that a process is spontaneous when the change in free energy is negative.

Hence;

∆G= ∆H - T∆S is expected to give us a negative value.

However, even when the overall dissolution process is endothermic, the positive change in entropy due to increase in the number of particles in solution leads to a negative value of free energy thereby making the process spontaneous.

Therefore, some salts are soluble in water even though the overall process is endothermic and the solution becomes colder during dissolution due to increase in entropy.