Measuring energy chgs
The measure of the average kinetic energy of particles.
What is Temperature?
Is making bonds endothermic or exothermic?.
exothermic
a compound with ______ energy is more stable than a compound with _______ energy. higher/lower
lower, higher
These enthalpy (energy) changes occur when chemical bonds are formed and broken.
What is energy is released when bonds are formed and absorbed when they are broken?
The enthalpy change for this reaction:
2HF --> H2 + F2
Bond energies are as follows: H-H: 430 F-F: 155 H-F: 565
What is +545 kJ?
Type of reaction where heat energy transferred from a system (chemical reaction) to the surroundings – the surroundings get hotter.
What is an Exothermic reaction?
_______ of ________ is the energy absorbed or released by any reaction
heat of reaction, also known as enthalpy change
The enthalpy change for the reaction below:
2CO (g) + O2 (g) --> 2CO2 (g)
Rxn 1: 2C(s) + O2(g) -->2CO (g) -222 kJ/mol
Rxn 2: C(s) + O2(g) --> CO2(g) -394 kJ/mol
What is -566 kJ/mol?
Needed to calculate the heat absorbed by a sample.
I - mass of the sample
II - density of the sample
III - specific heat capacity of the sample
What is I and III only?
The enthalpy change for the reaction of ethyne and hydrogen.
C2H2(g) + 2H2(g) --> C2H6(g)
Use information from table 10 of data booklet.
What is -287 kJ/mol?
The form of energy that flows from something at a higher temperature to something at a lower temperature.
What is Heat?
What is the value for the change in enthalpy of an exothermic reaction?
Negative (<0)
The enthalpy change of the following reaction.
MnO2(s) + C(s) --> Mn(s) + CO2(g)
Rxn 1: C(s) + O2(g) --> CO2(g) -390 kJ/mol
Rxn 1: Mn(s) + O2(g) --> MnO2(s) -520 kJ/mol
What is +130 kJ/mol?
The correct statement about the energies of this reaction:
Ba(OH)2(s) + 2NH4SCN(s) --> Ba(SCN)2(aq) + 2NH3(g) + 2H2O(l)
What is the reaction is endothermic and the change in enthalpy is positive?
CH4 + 2O2 ----> CO2 + 2H2O delta H = -213
is this exothermic or endothermic? are the products or reactants higher in energy?
exothermic, products
What type of reaction occurs when a system (chemical reaction) takes in heat energy from the surroundings – the surroundings get cooler?
What is name of a reaction where the products are less stable than the reactants?
Endothermic
The enthalpy change of the following equation.
2S(s) + 3O2(g) --> 2SO3(g)
Rxn 1: S(s) + O2(g) --> SO2(g) -300 kJ
Rxn 2: 2SO2(g) + O2(g) --> 2SO3(g) -200 kJ
What is -800 kJ?
Relationship between products and reactants focusing on stability in an endothermic reaction.
What is reactants are more stable than products and the enthalpy change is positive?
What is bond-breaking requiring energy (endo) and enthalpy change is positive - and - bond-making releases energy (exo) and enthalpy change is negative.
Explanation of why the changes in enthalpy of exothermic and endothermic reactions are either negative or positive.
Exothermic reactions have negative changes in enthalpy because heat is going out - making bonds.
Endothermic reactions have positive changes in enthalpy because heat is being absorbed inward - breaking bonds.
what law states that energy cannot be created or destroyed?
the law of conservation of energy
The definition of average bond enthalpy.
What is the energy required to break (a mole of) bonds in the gaseous state/ energy given out when (a mole of ) bonds are made in the gaseous state or average value from a number of similar compounds?
CH4 + H2O --> 3H2 + CO +210 kJ
The energy change that occurs when 1 mol of hydrogen is formed in the reaction above.
What is 70 kJ of energy are absorbed from the surroundings?
The reason that all bond enthalpies are positive values.
What is bond enthalpies are defined in terms of breaking bonds and therefore, have positive values due to being endothermic and requiring energy?