Question

please help me undersatnd how to solve the following two probekms below, thank you:

What's change in enthalpy at 25 degrees Celsius and 1 atm for the production of 1. 0.345 mol of iron (III) oxide? 4Fe(s)+302(g)-> 2F€2O3(s); AH= -1651 kJ A)-570. kJ B)-285 kJ C)-1140 D)285 kJ E)570. kJ 2) Given the thermochemical equation 2A1203(s) 4Al(s)+302(g); AH = 3352kJ find AHH for the following reaction. 8Al(s)602(g)-»4A1203(s) a) 838 kJ b)1676 kJ c)-6704 kJ d)1676 kJ e) 6704 kJ

Answer 1

1)

In reaction,

When 2 mol of Fe2O3 is produced, change in enthalpy = -1651 KJ

So,

When 0.345 mol of Fe2O3 is produced, change in enthalpy = -1651*0.345/2 = -285 KJ

Answer: -285 KJ

2)

2nd reaction = -2*1st reaction

So,

ΔH2 = -2* ΔH1

= -2*(3352 KJ)

= -6704 KJ

Answer: c