Energy changes and Covalent bonds - DF

Question 1

Bond breaking - energy

Answer 1

energy must be put in to break a bond so it is endothermic

Question 2

Bond making - energy

Answer 2

energy is given out when a bond is made so it is exothermic

Question 3

Bond enthalpy value definition (breaking)

Answer 3

energy needed to break a particular type of covalent bond for one mole of bonds in a gaseous state is called bond enthalpy and is always positive

Question 4

Bond enthalpy value definition (making)

Answer 4

to make 1 mole of the same bond will be the same value as breaking but negative

Question 5

Bond strengths - the bigger the bond enthalpy value the

Answer 5

shorter the bond length

Question 6

As double and triple bonds are stronger than single bonds what does this mean

Answer 6

they are shorter

Question 7

How to work out if a reaction is endothermic or exothermic using bond enthalpy vlaues

Answer 7

if the products have stronger bonds than the reactants more energy is given out making their bonds than had to be put in breaking the reactant bonds, so the reaction will be exothermic

Question 8

Why aren’t the enthalpy values exact

Answer 8

we used bond enthalpy values which are averages
for bond enthalpy calculations everything is he gaseous state, for standard enthalpy change values things will be in their standard states

Question 9

Why does fuel give out energy when it burns (bond breaking and making)

Answer 9

energy is taken in to break bonds in the reactant molecules but more energy is given out when bonds in the product molecules are made

Question 10

Butane and methylpropane are isomers - why are their enthalpy change values similar

Answer 10

they have the same number and type of bonds which need breaking and the same number and type of bonds being made