q = mass air(in g) x specific heat air x delta T
Solve for q (which is delta H)
Convert to g of the salt to give that delta H.
Glauber's salt undergoes a phase transition according to the following equation:
Na2SO4*10H2O(s)--> Na2SO4*10H2O(l) ∆H = 74.4 kJ/mol
Calculate the mass (g) of Glauber's salt (use the masses to two decimal places found in the front of your text) needed to lower the temperature of air in a room by 7.8oC. The mass of air in the room is 578 kg; the specific heat of air is 1.2J/g-C.
I'm not sure what formula to use here, can i get a hint please?
4 answers
Q=578000(1.2)(7.8)= 5410080.
Im not sure I understand the last part with the grams of the salt.
Im not sure I understand the last part with the grams of the salt.
You're right so far. 5.41E6 J = 5.41E3 kJ.
molar mass Glauber's salt is 322 so here is what you have.
322 g salt absorbs 74.4 kJ. So how many g will it take to absorb 5.41E3 kJ. That will be
322 x (5.41E3 kJ/74.4 kJ) = ? g of the salt.
molar mass Glauber's salt is 322 so here is what you have.
322 g salt absorbs 74.4 kJ. So how many g will it take to absorb 5.41E3 kJ. That will be
322 x (5.41E3 kJ/74.4 kJ) = ? g of the salt.
Thank you so much for all your help.
2 answers