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# Energy, q, w, Enthalpy, and Stoichiometry II and Specific Heat

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Problem 1 - Energy, q, w, Enthalpy, and Stoichiometry
Consider the following reaction:

2Mg(s)+O2(g)>>2MgO(s)&#916;H = -1204kJ

1) Is this reaction exothermic or endothermic?

2) Calculate the amount of heat transferred when 2.1 g of Mg(s) reacts at constant pressure.

3)How many grams of MgO are produced during an enthalpy change of -94.0 kJ ?

4)How many kilojoules of heat are absorbed when 7.80 g of MgO(s) is decomposed into Mg(s) and O2(g) at constant pressure?

Problem 2 - Specific Heat

The specific heat of iron metal is 0.450 J/g*K
How many J of heat are necessary to raise the temperature of a 1.10 - Kg block of iron from 26.0 Celsius degrees to 88.0 Celsius degrees?

https://brainmass.com/chemistry/reaction-stoichiometry/energy-enthalpy-stoichiometry-specific-heat-306973

#### Solution Preview

Problem 1 - Energy, q, w, Enthalpy, and Stoichiometry
Consider the following reaction:

2Mg(s) + O2(g) >> 2MgO(s) ΔH = -1204kJ

1) Is this reaction exothermic or endothermic?
Since ΔH is negative, the reaction is exothermic.

2) Calculate the amount of heat transferred when 2.1 g of Mg(s) reacts at constant pressure.