Flashcards in Energy Changes Deck (67)
How do you find the mass of a solution?
Volume x density (assume density is 1 unless told otherwise)
What is the specific heat capacity
The amount of energy that is needed to raise the temperature of a solution by 1 degree
What is the specific heat capacity of water?
When do you not add the masses together and when do you?
Don't add the mass of a solid reactant to the mass of the solution, but if two solutions then add them together
What is the equation for molar enthalpy change?
Molar enthalpy change (kJmol-1) = - heat energy transferred / no. of moles
Delta H (triangle H) = -Q / n
Equation to find energy change
Energy change (J) = mass of solution (g) x specific heat capacity (J/g/•C) x temp change
Q= m x c x Delta T
How does temperature, energy, and molar enthalpy change in an exothermic reaction
Heat energy transferred is positive
Molar enthalpy change is negative
How does temperature, energy, and molar enthalpy change in an endothermic reaction
Temperature decreases, heat energy is negative, molar enthalpy is positive
What are exothermic reactions and what is the energy of their products like in relation to the reactants
Exothermic reactions release energy into their surroundings
Products have a lower energy than the reactants
What are endothermic reactions and what are their products like in relation to their reactants
Endothermic reactions absorb energy from their surroundings
Products have a higher energy than the reactants
Example of an exothermic reaction
N2 + 3H2 = 2NH3 (Haber process)
Example of an endothermic reaction
H2 + I2 = 2HI
KNOW HOW TO DRAW ENERGY CHANGE DIAGRAMS
What is the bond energy
Bond energy is the energy required to break one mole of covalent bonds.
Equation for molar enthalpy change from bond energies
Molar enthalpy change = Sum of bonds broken - sum of bonds made
What happens when bonds are broken
It requires energy and is an endothermic process
What happens when bonds are made
Energy is produced, it's an exothermic process
What is the relative atomic mass (Ar)
The weighted average sum of all the isotopes of an element
Equation for relative atomic mass
Ar = sum (isotope mass x abundance) / 100
Equation for Mr
Sum of Ar
Equation for moles
Mass / Mr
What is Avogadro's Law
Equal volumes of gases at the same temperature and pressure contain equal numbers of molecules. This means that one mole of any gas will occupy the same volume at the same temperature and pressure.
What is the "molar volume" of one mole of any gas?
Equation to work out moles of a gas
Mols of a gas = volume (cm3) / 24000 (cm3)
What is a redox reaction?
A reaction in which one species is oxidised and another is reduced
What is oxidation
The loss of electrons, loss of hydrogen, addition of oxygen
What is reduction
The gain of elections, addition of hydrogen, loss of oxygen
What is the full equation for magnesium + copper oxide
Mg + CuO = MgO + Cu
What is the ionic equation for magnesium + copper oxide
Mg + Cu 2+ = Mg 2+ + Cu