The reaction is
2H₂(g) + O₂(g) ---> 2H₂O
Thus as per balanced equation two moles of hydrogen will react with one moles of oxygen.
There is a directly relation between moles and volume. [One mole of each gas occupies 22.4 L of volume at STP]
Thus we can say that two unit volume of hydrogen will react with one unit volume of oxygen
Now as we have started with equal units of volume of both oxygen and hydrogen, half of oxygen will be consumed against complete volume of hydrogen
so the gas which will remain in excess is oxygen
If the value of H is positive, it means you have to add that much heat to complete the reaction. If H is negative, it means that much heat is released during the chemical process. Because it is -73 kJ, 73 kJ of heat are released in the reaction.
Hydrogen atom and chlorine atom makes hydrogen chloride molecules.
It is the lowest point in the substance and possesses chemical elements. Atoms don't exist on their own; instead, they combine to create ions and molecules, which combine to create the substances that we can see, feel, and touch.
One or more atoms joined together by covalent (chemical) connections make up molecules. Atoms can be imagined as circles with a central nucleus (consisting of protons and neutrons) and one or more concentric circles surrounding it that represent the "shells" or "levels" in which the electrons surrounding the atom's nucleus are located as well as markings that distinguish the electron. every level
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