Reacting Substances Flashcards
In order to react particles must
collide wIth enough energy
what is the activation energy.
The minimum amount of energy that particles must have to react.
In an exothermic reaction, energy is ———— the surroundings. The temperature of the surroundings therefore ———. The energy of the reactants is —— than the energy of the products.
released to, increases, higher
In endothermic reactions, the energy needed to break existing bonds is —— than the energy released when new bonds are formed
Greater
In exothermic reactions, the energy needed to break existing bonds is —— than the energy released when new bonds are formed
Less
The amount of energy required to make or break a bond is called the
Bond energy
Bond energy is measured in
kilojoules per mole or kcal/ mol
The enthalpy change can be described in what equation
energy change = energy in – energy out.
What does enthalpy mean
the measurement of energy in a thermodynamic system
in —– reactions more energy is released making new bonds than is taken in to break old bonds. this is indicated by a —– enthalpy change
Exothermic, negative.
in —– reactions less energy is released making new bonds than is taken in to break old bonds. this is indicated by a —– enthalpy change
Endothermic, positive
An electrochemical cell is a cell that uses ————— to generate electricity
Chemical reactions
In order to make an electrochemical work we need two metals which are
An electrolyte and a wire
the more reactive metal will become the —— of the end of the cell
anode (negative electrode)
the less reactive metal will become the ‘’ of the end of the cell
cathode (positive electrode)
The electrons will flow from the —— reactive metal to the —— generating a current
More, less
what is needed to make up an electrochemical cell
Electrochemical Cells are made up of two half-cells, each consisting of an electrode which is dipped in an electrolyte
Fuel cells are cells supplied by an external source of fuel (eg. ——) and ——— or ——.
They work by electrochemically —— the fuel.
The equation for the chemical reaction inside fuel cells is
2H2 + 2O2− → 2H2O + 4e
What are the advantages of using fuel cells?
-Clean Energy
-Versatility
-Longevity
What are the disadvantages of using fuel cells?
-Safety
- expensive
-Efficiency
In hydrogen fuel cells, hydrogen reacts with oxygen to form water. Water is formed at the
the cathode
The half equation for the reaction of hydrogen and water at the —— in a hydrogen fuel cell is ——. ++
cathode, 2H₂O (l) + 2e⁻ ⇌ H₂ (g) + 2OH⁻ (aq)
The half equation for the reaction of hydrogen at the —- in a
