Endothermic reactions enthalpy changes

Question 1

reaction is endothermic when

Answer 1

the products have more energy than the reactants

Question 2

Heat energy is …………..by the reaction from the surroundings

Answer 2

absorbed

Question 3

The temperature of the environment ……………..- this can be measured with a thermometer

Answer 3

decreases

Question 4

The energy of the system …………

Answer 4

increases

Question 5

There is an enthalpy …………… during the reaction so ΔH is ……………..

Answer 5

increase

positive

Question 6

It is important to specify the physical states of each species in an equation when dealing with enthalpy changes as any changes in state can cause very large changes of enthalpy. For example:

NaCl (s) → Na+ (aq) + Cl- (aq) ΔH = +4 kJ mol-1

NaCl (g) → Na+ (g) + Cl- (g) ΔH = +500 kJ mol-1

Also, remember that the system is the substances that are reacting (i.e. the reaction itself) and the surroundings is everything else (e.g. the flask the reaction is taking place in).