Phy Chem.

1.a) I think it may be Ammonium Nitrate.

Ammonium Nitrate dissolving in water is endothermic.

b).defrosting is endothermic.

2.K.E. of a gas depends only on temperature.
a)B.
b)C.H₂ is lighter in mass and hence moves faster, since the average K.E. are the same.

2013-11-25 17:33:09 補充：
I am sure that dissolving Ammonium Nitrate is endothermic.

But I don't know about aluminium nitrate.

For question 2b :

K.E. of the gas depends on absolute temperature.

(273+25) / 273 = 1.09. This is not as important as Oxygen(32)/Hydrogen(2) = 16

1. Classify each of the following processes as exothermic or endothermic.
Note: the system being considered is bracketed.

a.) when aluminium nitrate is added to water, the (solution) gets cooler
endothermic (the cooler solution needs to be warmed up to allow more salt to dissolive)

b.) defrosting a frozen chicken by using a microwave cooker.
endothermic (energy input process)

2. Consider 3 identical flasks filled with different gases.
A: CO at 1 atm and 0 deg.
B: O2 at 0.5 atm and 25 deg.
C: H2 at 0.25 atm and 0 deg.

a). in which flask will the molecules have the greatest average KE?
A (largest gas pressure)

b). in which flask will the molecules have the greatest velocoty?
C (similar pressure but small molecular mass; it gives the largest velocity)