Enthalpy changes Flashcards
What is the enthalpy change of solution?
the enthalpy change when one mole of a compound is completely dissolved in water to form its aqueous ions
CaCl2(s) –> C+2(aq) + 2Cl-
What is the enthalpy change of hydration?
when one mole of gaseous ions forms one mole of aqueous ions
Na+(g) –> Na+(aq)
What are the equations used for enthalpy change?
Q = mc/\T
/\H = (Q/1000)/n
What is lattice enthalpy?
the enthalpy change when one mole of an ionic compound is formed from its gaseous ions
Ca+2(g) + 2Cl-(g) –> CaCl2(s)
What happens to the ionic bond depending on the enthalpy change?
the more exothermic (-) the lattice enthalpy, the stronger the ionic bond
the more endothermic (+) the lattice enthalpy, the weaker the bond
What is the enthalpy change of atomisation?
the enthalpy change when 1 mole of gaseous atoms is formed from an element in its standard state
Mg(s) –> Mg(g)
What is first electron affinity?
the enthalpy change when one electron is added to each atom in one mole of gaseous atoms to form one mole of gaseous -1 ions
O(g) + e- –> O-(g)
What is second electron affintiy?
the enthalpy change when one electron is added to each atom in one mole of gaseous -1 ions atoms to form one mole of gaseous -2 ions
O(g) + e- –> O-(g)
What is enthalpy change of formation?
the enthalpy change when one mole of a compound is formed in its standard state from it elements in their standard states
Mg(s) + 1/2O2(g) –? MgO
How do you solve mini born haber cycles?
fill in the arrows with the right enthalpy change
use the values given to solve the unknown
if the arrow is pointing the right way, use the sign given. if the arrow is in the wrong direction, use the opposite sign
What is the outline for an enthalpy change of hydration answer from x to y?
- ionic charge (same, increase, decrease)
- ionic radius (same, larger, smaller)
- charge density (same, increase, decrease) (charge/radius)
- attraction to water (same, increases, decreases)
- enthalpy of hydration more/less exothermic
