Be sure to answer all parts. Consider the following balanced thermochemical equation for the decomposition of the mineral magne MgCO3 (s) → MgO (s) + CO2 (g) ΔHrxn = 117.3 kJ (a) Is heat absorbed or released in the reaction? released absorbed (b) What is ΔHrxn for the reverse reaction? kJ (c) What is ΔH when 5.10 mol of CO2 reacts with excess MgO? kJ (d) What is ΔH when 41.0 g of CO2 reacts with excess MgO?

a) the system absorbed heat

b) ΔHrxn = - 117.3 kJ

c) ΔH = 603.33 kJ

d) ΔH = 109.3 kJ

Explanation:

Step 1: The balanced equation

MgCO3 (s) → MgO (s) + CO2 (g)

Step 2: Data given

ΔHrxn = 117.3 kJ

(a) Is heat absorbed or released in the reaction?

When ΔHrxn > 0 means the system absorbed heat. This is called an endothermic reaction.

b) What is ΔHrxn for the reverse reaction?

ΔHrxn = - 117.3 kJ, The reversed reaction is exothermic

(c) What is ΔH when 5.10 mol of CO2 reacts with excess MgO?

When 1 mol of CO2 reacts ΔH = 117.3 kJ

When 5.10 mo of CO2 reacts ΔH = 117.3 * 5.10 = 603.33 kJ

(d) What is ΔH when 41.0 g of CO2 reacts with excess MgO?

Moles = mass / Molar mass

Moles = 41.0 grams / 44.01 g/mol = 0.932 moles

For 1 mol ΔH = 117.3 kJ

For 0.932 moles ΔH = 117.3 * 0.932 = 109.3 kJ