Hess's law flashcard

Front

What is Hess's Law?

Back

Hess's Law states that the total enthalpy change for a chemical reaction is the same, regardless of the number of steps the reaction takes.

Front

What is an exothermic reaction?

Back

An exothermic reaction is a chemical reaction that releases energy in the form of heat to the surroundings.

Front

What is an endothermic reaction?

Back

An endothermic reaction is a chemical reaction that absorbs energy from the surroundings, usually in the form of heat.

Front

What does ∆H represent in a chemical reaction?

Back

∆H represents the change in enthalpy, or heat content, of a system during a chemical reaction.

Front

If a reaction has a negative ∆H, what type of reaction is it?

Back

It is an exothermic reaction.

Front

If a reaction has a positive ∆H, what type of reaction is it?

Back

It is an endothermic reaction.

Front

What is the enthalpy change for the reaction: MgO(s) + H2(g) → Mg(s) + H2O(g)?

Back

+360 kJ.

Front

How do you calculate the enthalpy change using Hess's Law?

Back

By adding the enthalpy changes of the individual steps of a reaction.

Front

What is the enthalpy change for the formation of 1 mole of H2O(g)?

Back

-242 kJ.

Front

What is the enthalpy change for the reaction: N2O4(g) → 2N(g) + 4O(g)?

Back

1933 kJ.