Energetics Flashcards
What is enthalpy change?
Enthalpy change is the amount of heat change taken in or out given during any change in a system provided the pressure is constant.
What is an exothermic reaction?
An exothermic reaction is when energy is transferred from they system to the surroundings. The products have less energy than the reactants.
In an exothermic reaction is the enthalpy change negative or positive ?
Negative
What are common oxidation exothermic processes?
The combustion in fuels and oxidation of carbohydrates such as glucose in respiration.
What is an endothermic reaction?
Energy is transferred from the surroundings to the system. The products have more energy than the reactants. They require an input of heat energy.
What is an example of an endothermic reaction?
Thermal decomposition of calcium carbonate.
What is the standard change of formation?
The standard enthalpy change of formation is the enthalpy change when 1 mole of a compound is formed from its constituent elements under standard conditions when it is in its standard state.
What is the symbol for the standard change of formation?
ΔH°f
What is the definition of the standard change of combustion?
The enthalpy change of combustion is the standard change when one mole of a substance is combusted completely in oxygen under standard conditions when all the reactants and products are in its standard states.
What is the symbol for the standard state of combustion?
ΔH°c
What equation is used for measuring the enthalpy change for a reaction experimentally?
energy change= mass of solution × heat capacity × temperature change .
Q (J)= m (g)c (J g^-1K^-1) ΔT (K)
q = mcΔT
What is Hess’s law?
A law that states that enthalpy change for a reaction is independent of the route by which the chemical change takes place.
What rules do measuring enthalpy change have?
For measuring enthalpy change if the temperature increases, the reaction is exothermic and the answer is given a minus sign.
How many sig figs should be used?
The amount shown or used in the data given in the question?
