Umm its not a i think... lemme see lol
Answer:
The mass of oxygen is 12.10 g.
Explanation:
The decomposition reaction of potassium chlorate is the following:
2KClO₃(s) → 2KCl(s) + 3O₂(g)
We need to find the number of moles of KClO₃:

Where:
m: is the mass = 30.86 g
M: is the molar mass = 122.55 g/mol
Now, we can find the number of moles of O₂ knowing that the ratio between KClO₃ and O₂ is 2:3
Finally, the mass of O₂ is:

Therefore, the mass of oxygen is 12.10 g.
I hope it helps you!
Answer:
I would use calorimetric to determine the specific heat and I would measure the mass of a sample
Explanation:
I would use calorimetry to determine the specific heat.
I would measure the mass of a sample of the substance.
I would heat the substance to a known temperature.
I would place the heated substance into a coffee-cup calorimeter containing a known mass of water with a known initial temperature.
I would wait for the temperature to equilibrate, then calculate temperature change.
I would use the temperature change of water to determine the amount of energy absorbed.
I would use the amount of energy lost by substance, mass, and temperature change to calculate specific heat.