Calculate the molality of a 20.0 percent by weight aqueous solution of nh4cl. (molecular weight: nh4cl = 53.5)

Explanation:

If we have a 20% by weight solution indicates that in 100 g of solution we have 20 g of . So, in the 100 g of solution we will have 80 g of (100-20= 80). If we remember the molality equation:

On this case the solute is , so we have to convert from g to mol using the molar mass:

Then we have to calculate the Kg of solvent (), so:

Finally, we have to divide these two values:

answer: semi-infinite solid initially at a uniform temperature of 400 ◦c is cooled at its surface by convection. the cooling fluid at a constant temperature of 200 ◦c has a convective coefficient (ha) of 250 w/m2.k. the physical properties of the solid: k = 20 w/m.k and α = 4 * 10-5  m2/s. using δx = 0.04 m and δt = 10 s. write the finite difference equations describing the transient heat transfer of the first five δx and the temperature profile after 30 s.