Ammonia reacts with oxygen according to the equation 4n h 3 (g)+5 o 2 (g)→4no(g)+6 h 2 o(g),δ h rxn =−906 kj calculate the heat (in kj ) associated with the complete reaction of 155 g of n h 3 .

-2.07 × 10³ kJ

Explanation:

Let's consider the following balanced equation.

4 NH₃(g) + 5O₂(g) → 4 NO(g) + 6H₂O(g)    ΔHrxn =−906 kJ

The enthalpy of reaction is -906 kJ, that is, 906 kJ are released upon the reaction of 4 moles of NH₃. Taking into account that the molar mass of NH₃ is 17.0 g/mol, the heat associated with the complete reaction of 155 g of NH₃ is:

2fe + 3h2so4 -> fe2(so4)3 + 3h2

it is necessary to balance equations in order to get the proper amount of reactants as well as products in order not to make a miscalculation.

you cannot change the subscripts as that would change the substance itself. for instance, diatomic elements such as h2 only have the subscript two when a gas. another example would be so4, if you were to change the subscript, the element would no longer be sulfate.

we change the coefficients instead as that only changes the number of molecules rather than the substance itself.

hope this !

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