Answer to Question #162483 in General Chemistry for Elizabeth Godfrey

Question

A 2000 g ingot of iron (specific heat capacity 0.45 J/gC) originally at -200 degrees C absorbs the energy released by burning a sample of 40.0 g of wood (releases 21.2 MJ/kg).

6) How much energy in Kilojoules (kJ) was released by the burning wood? (do not use scientific notation and watch your sig figs) 

[hint: the enthalpy of combustion is given as 21.2 MEGA Joules per KILOGRAM, but we want the answer (after taking into account the amount of wood) in just JOULES]

1 MJ = 1x10^6 J (it's a nice trick to remember that Mega is 1 million of a base unit... M for million... lol)

Answer 1

It is given energy released by burning wood is 21.2MJ/Kg

so it is equal to 21.2 KJ/g .

so by burning 40 g of wood it will release 21.2x40 KJ = 848 KJ