Respuesta :
Answer:
-7.34 kilo Joules is the change in enthaply when 20.0 grams of nitrogen triiodide decomposes.
Explanation:
Mass of nitrogen triiodide = 20.0 g
Moles of nitrogen triiodide = [tex]\frac{20.0 g}{395 g/mol}=0.05063 mol[/tex]
[tex]2NI_3(s)\rightarrow N_2(g)+3I_2(g), \Delta H_{rxn}=-290.0 kJ[/tex]
According to reaction, 2 moles of nitrogen triiodide gives 290.0 kilo Joules of heat on decomposition ,then 0.05063 moles of nitrogen triiodide will give :
[tex]\frac{-290.0 kJ}{2}\times 0.05063=-7.34 kJ[/tex]
-7.34 kilo Joules is the change in enthaply when 20.0 grams of nitrogen triiodide decomposes.
Taking into account the definition of enthalpy of a chemical reaction, the quantity of heat released when 20.0 g of NI₃ decomposes is 7.34 kJ.
What is enthalpy of a chemical reaction
The enthalpy of a chemical reaction as the heat absorbed or released in a chemical reaction when it occurs at constant pressure. That is, the heat of reaction is the energy that is released or absorbed when chemicals are transformed into a chemical reaction.
The enthalpy is an extensive property, that is, it depends on the amount of matter present.
Change in enthaply
In this case, the balanced reaction is:
2 NI₃ → N₂ (g) + 3 I₂(g)
and the enthalpy reaction ∆H° has a value of -290 kJ.
This equation indicates that when 2 moles of NI₃ decomposes, 290 kJ of heat is released.
Now 20.0 g of NI₃ decomposes. Being the molar mass of NI₃ 395 g/mole, the moles of NI₃ that decomposes is calculated as:
[tex]moles= \frac{20 g}{395 \frac{g}{mole} } =[/tex] 0.05063 moles
When 0.05063 moles of NI₃ decomposes, then you can apply the following rule of three: if 2 moles of NI₃ releases 290 kJ of heat, 0.05063 moles of NI₃ releases how much heat?
[tex]heat=\frac{0.05063 molesx290 kJ}{2 moles}[/tex]
heat= 7.34 kJ
Finally, the quantity of heat released when 20.0 g of NI₃ decomposes is 7.34 kJ.
Learn more about enthalpy of a chemical reaction:
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