It might change because of the amout of rain that fell in the year and the melting of ice which allows the water amount to increase
<u>Answer:</u> The formation of given amount of oxygen gas results in the absorption of 713 kJ of heat.
<u>Explanation:</u>
To calculate the number of moles, we use the equation:

Given mass of oxygen gas = 83 g
Molar mass of oxygen gas = 32 g/mol
Putting values in above equation, we get:

For the given chemical equation:

<u>Sign convention of heat:</u>
When heat is absorbed, the sign of heat is taken to be positive and when heat is released, the sign of heat is taken to be negative.
By Stoichiometry of the reaction:
When 3 moles of oxygen gas is formed, the amount of heat absorbed is 824.2 kJ
So, when 2.594 moles of oxygen gas is formed, the amount of heat absorbed will be = 
Hence, the formation of given amount of oxygen gas results in the absorption of 713 kJ of heat.
Iron has TWO valence electrons......
Answer:
compounds , because they're combined
Answer:
The emission spectrum is formed when the electrons of a particular atom absorb energy and are excited (in this case by heating), reaching higher energy levels.
You can see it for example with an experiment where we light alcohol mixed with banana chips (it has potassium). The burning alcohol emits heat that makes potassium atoms excite and these in turn emit something red, orange light. If we add for example boric acid you see a green light.
Explanation: