for the reaction
4NH3(g) + 5O2(g) <--> 4NO(g) + 6H2O(g)
if H = -950kJmol-1, does that mean it's an exothermic reaction?
Ooops pressed Post too quickly.
Yes it is exothermic. Delta H is negative so heat is lost from the system. If delta H is positive a reaction is endothermic as it is gaining heat.
Yes, that is correct. A negative value for ΔH indicates that the reaction is exothermic. In an exothermic reaction, heat is released from the system to the surroundings. In this case, the negative value of ΔH (-950 kJ/mol) indicates that the reaction releases 950 kJ of heat per mole of reaction.
To determine whether the reaction is exothermic or endothermic, you need to look at the sign of the enthalpy change (ΔH) of the reaction. In this case, the given value for ΔH is -950 kJ/mol, which is negative.
A negative ΔH indicates an exothermic reaction. In an exothermic reaction, heat is released from the system to the surroundings. This means that the reaction has a net energy release, and temperature of the surroundings may increase.
On the other hand, a positive ΔH would indicate an endothermic reaction. In an endothermic reaction, heat is absorbed by the system from the surroundings. This means that the reaction has a net energy gain, and the temperature of the surroundings may decrease.
In summary, since the given ΔH value is negative (-950 kJ/mol), the reaction of 4NH3(g) + 5O2(g) ⇌ 4NO(g) + 6H2O(g) is indeed exothermic.