Exothermic and endothermic reactions

Question 1

Describe exothermic reactions

Answer 1

Releases energy into surroundings, has negative change in enthalpy, is normally spontaneous, energy bond formation>energy of bond breaking

Question 2

Example of an exothermic equation

Answer 2

Harber process (producing ammonia)

N2(g) + 3H2(g) <> 2NH3(g) (change H-92kjmol)

Question 3

Examples of exothermic reactions

Answer 3

Combustion - burning stuff
Respiration - coverting glucose and oxygen into c02 h20 energy in body
Neutralisation - acid + base to form water and salt, heat is released

Question 4

Describing exothermic reactions

Answer 4

Absorbs energy from surroundings
Has positive change in enthalpy
Normally requires heat or energy input to be spontaneous
Energy bond formation < the energy bond breaking

Question 5

Endothermic equations

Answer 5

CO2(g) + H20(l) -> C6H12O6(s) + O2(g) (change H +2814 kjmol)

Question 6

Examples of endothermic reactions

Answer 6

Photosynthesis - plant absorbs sunlight
melting ice - Ice melts to form water (absorbs heat from surroundings)
thermal decomposition - calcium carbonate decompose into calcium oxide and c02 when heated. (requires absorption of heat)