In: Chemistry
Consider the following reaction:
2Mg(s)+O2(g)→2MgO(s)ΔH=−1204kJ
Calculate the amount of heat transferred when 3.54 g of Mg(s) reacts at constant pressure.
How many grams of MgO are produced during an enthalpy change of -237 kJ ?
How many kilojoules of heat are absorbed when 40.1 g of MgO(s) is decomposed into Mg(s) and O2(g) at constant pressure?
2Mg + O2 ------------> 2MgO : delta H = -1204 kJ
When 2 moles (2mol x 24g/mol) of Mg reacts heat transferred = 1204 kJ
If 3.54g of Mg is used , the heat transferred = 3.54g x 1204 kJ /2x24 g
=88.795 kJ
2) When the enthalpy change is 1204 kJ the mass of Mg reacted = 2x24 g
If the energy change is 237 kJ , mass of Mg reacted = 237 kJ x 2x24 g /1204kJ =9.45 g
3) 2MgO --------------------> 2Mg + O2 . DElta H = +1204kJ
2molx40.3g /mol of MgO on decomposition absorbs 1204 kJ of heat
If 40.1 g of MgO is decomposed , the heat absorbed = 40.1gx 1204kJ /2x40.3g
=599 kJ