Molality of the solution is defined as the number of moles of a substance dissolved divided by the mass of the solvent:
Molality = number of moles / solvent mass
From the concentration of 39% (by mass) of HCl in water, we construct the following reasoning:
in 100 g solution we have 39 g hydrochloric acid (HCl)
number of moles = mass / molecular weight
number of moles of HCl = 39 / 36.5 = 1.07 moles
solvent (water) mass = solution mass - hydrochloric acid mass
solvent (water) mass = 100 - 39 = 61 g
Now we can determine the molality:
molality = 1.07 moles / 61 g = 0.018
Answer:
Sleet and hail, sleet are tiny drops of water that freeze when it rains. Hail forms when a thunderstorm lifts a water droplet above the freezing level.
Explanation:
Deforestation and inappropriate agriculture otherwise known as over farming are factors of and causes of desertification.
Answer: The standard enthalpy of formation of 
is -252.1 kJ/mol.
Explanation:
The balanced chemical reaction is,
The expression for enthalpy change is,
![\Delta H=[n\times H_f_{products}]-[n\times H_f_{reactantss}]](https://tex.z-dn.net/?f=%5CDelta%20H%3D%5Bn%5Ctimes%20H_f_%7Bproducts%7D%5D-%5Bn%5Ctimes%20H_f_%7Breactantss%7D%5D)
Putting the values we get :
![\Delta H=[2\times H_f{Fe}+3\times H_f{H_2O}]-[1\times H_f{Fe_2O_3}+3\times H_f{H_2}]](https://tex.z-dn.net/?f=%5CDelta%20H%3D%5B2%5Ctimes%20H_f%7BFe%7D%2B3%5Ctimes%20H_f%7BH_2O%7D%5D-%5B1%5Ctimes%20H_f%7BFe_2O_3%7D%2B3%5Ctimes%20H_f%7BH_2%7D%5D)
![67.9kJ=[(2\times 0)+(3\times H_f{H_2O})]-[(1\times -824.2kJ/mol)+3\times 0kJ/mol)]](https://tex.z-dn.net/?f=67.9kJ%3D%5B%282%5Ctimes%200%29%2B%283%5Ctimes%20H_f%7BH_2O%7D%29%5D-%5B%281%5Ctimes%20-824.2kJ%2Fmol%29%2B3%5Ctimes%200kJ%2Fmol%29%5D)
Thus standard enthalpy of formation of is -252.1 kJ/mol.
It is letter C: Continental crust is thicker than oceanic crust.
