Question

2) What is the change in enthalpy when 3.400 moles of aluminum react with excess ammonium nitrate (NH4NO3)

Answer 1

The enthalpy change with the reaction of 3.4 moles of aluminum in the reaction is -3045 kJ. The reaction is exothermic in nature.

What is an exothermic and endothermic reaction?

The reaction in which the energy is released and the value of change in enthalpy is negative is an exothermic reaction. The reaction in which the energy is absorbed with the positive value of change in enthalpy.

For a balanced chemical reaction, for 2 moles of Aluminum reaction, the change in enthalpy has been -2030 kJ. The change in enthalpy for the reaction of 3.4 moles of aluminum is given as:

$\rm 2\;mol\;Al=-2030 \;kJ\\\\3.4\;mol\;Al=\dfrac{-2030}{2}\;\times\;3\;kJ\\\\ 3.4\;mol\;Al=-3045\;kJ$

The change in enthalpy for 3.4 moles of aluminum reaction is -3045 kJ. The reaction is exothermic in nature.

Learn more about exothermic reaction, here:

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Answer 2

Answer: See below

Explanation:

(i) 2AI + 3 NHANO3 → 3 N2+ 6 H2O + Al2O3  ΔH = -2030kJ

From stoichiometric coefiicients, it can be seen that:

When 2 moles of Al react, change in enthalpy =  -2030kJ

So, when 3.4 moles of Al react, change in enthalpy =  -(2030/2) x 3.4  kJ = -3451 kJ

Therefore, the change in enthalpy is -3451 kJ

(ii) The change in enthalpy is negative. This means heat is released during the reaction.

So the reaction is exothermic