C. 28 KJ
AMU of H2O2 = 2(1) + 2(16) = 34 g/mol
10 g / 34 g/mol = 0.294 mol H2O2
0.294 mol / H = 2 mol / 190 KJ
H = 28.9 KJ
Answer : At constant pressure work is done by the system on the surroundings.
Explanation :
Work done : Any quantity that flows across the boundary of a system during a change in its state and it completely convertible into the lifting of a weight in the surroundings.
Formula for work done is:

Sign convention :
- When volume expand then system work that means work done by the system.
w = (-ve)
- When volume compress then surrounding work that means work done on the system.
w = (+ve)
The given reaction is:

This is a evaporation process in which phase changes from liquid state to gaseous state at constant temperature.
At constant pressure, work depends only on volume.
In evaporation process, the volume expand that means work is done by the system on the surroundings.
Sign convention is, w = (-ve)
Thus, at constant pressure work is done by the system on the surroundings.
freezing. Think of what happens when you put water in the freezer
Each mole of substance contains 6.02 x <span>1023</span> component parts, in this case water molecules.
If you have 2.3 moles of water you will have 2.3 x 6.02 x <span>1023</span> which is 1.3846 x <span>1024</span> molecules.
Each molecule contains 2 hydrogen atoms, so the total number of hydrogen atoms in 2.3 moles of water will be 2 x 1.3846 x <span>1024</span> = 2.7692 x <span>1024</span>.
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