video 3 Flashcards
what is the major limitation of bond enthalpy calculations?
only works if products and reactants all only have covalent bonds
why can we not just use bond enthalpies for ionic substances?
because ionic bond strength depends on the temperature (ions move closer/further away), and don’t just have a fixed enthalpy change
why does covalent bond strength not change with temperature?
because it is the intermolecular forces that change, not the covalent bonds (they are super strong)
what do we measure the temperature of?
the water, since most of these reactions are done in solution
why doesn’t it work very well if the rate of reaction is slow?
because there is too much time for energy to be gained/lost
what is the equation to calculate the enthalpy change?
q = mass of chemical being heated/cooled x specific heat capacity x temperature change
why do we use a polystyrene cup?
because it is a much better insulator than a glass cup - to prevent any heat loss to the atmosphere
