5.1 Exothermic & Endothermic Reactions

Which is true about chemical energy changes?

	Reaction type	Energy flows	Temperature of surroundings
A	exothermic	to the surroundings	increases
B	exothermic	from the surroundings	decreases
C	endothermic	to the surroundings	decreases
D	endothermic	from the surroundings	increases

The reaction profile for making nitrogen monoxide, NO, is shown below:

 

What is the activation energy for this reaction?

Chlorine reacts with methane in sunlight.

 CH₄ + Cl₂  → CH₃Cl + HCl

The diagram below shows the displayed formulae for the reaction of chlorine with methane. 

 The table below shows the bond energies and the overall energy change in the reaction. 

 

	C-H	Cl-Cl	C-Cl	H-Cl	Overall energy change
Energy in kJ/mol	413	243	X	432	-122

 

What is the value of X?

How much energy is needed to break all the bonds in 0.025 g of nitrogen gas?

Relative atomic mass (Ar): N = 14

Bond	Bond energy in kJ/mol
NN	945

What is the reading on the following thermometer?

Endothermic reactions can be used in emergency sports injury treatment packs.

What is true about these packs?