Can someone please help me with this chemistry problem? ?

Question

Glauber's salt, sodium sulfate decahydrate (Na2SO4·10 H2O), undergoes a phase transition (that is, melting or freezing) at a convenient temperature of about 32°C. 
Na2SO4·10 H2O(s)  Na2SO4·10 H2O(l) ΔH° = 74.4 kJ 
As a result, this compound is used to regulate the temperature in homes. It is placed in plastic bags in the ceiling of a room. During the day, the endothermic melting process absorbs heat from the surroundings, cooling the room. At night, it gives off heat as it freezes. Calculate the mass of Glauber's salt in kilograms needed to lower the temperature of air in a room by 6.90°C at 1.0 atm. The dimensions of the room are 2.50 m  12.1 m  16.0 m, the specific heat of air is 1.2 J/g·°C, and the molar mass of air may be taken as 29.0 g/mol.

thank you!

Erin H · Accepted Answer

Go to UF? I'm the tutoring zone chem 1 semester+ teacher, whats up? haha

Ok so this problem gives you one thing you dont need and doesnt give you something you do need. You DO need the density of the air which (I looked it up) is 1.168kg/m^3. You DONT need the molar mass of the air.

First find the volume of the room. Then use the density to find the kg of air in the room. Then use MCT (using the kilograms) to find the heat the cooling down air lets off, your answer will be in KJ. With me so far?
Then the heat of formation of Glauber's salt is given as 74.4 kj/mol. take the answer you got before (in KJ) and divide by the heat of formation. This gives you moles of Glauber's salt. Then use the molar mass to convert to grams. Done.

The molar mass is 322g/mol (cuz I'm nice)

nobuko · Answer

Uf Tutoring Zone

Erika · Answer

Tutoringzone Uf

Anonymous · Answer

Given pressure and temperature plus the formula of a gas calculate it  density. Can someone give me an example with this information

Can someone please help me with this chemistry problem? ?

4 Answers