10 Baking soda (NaHCO3) decomposes when it is heated according to the equation below. How many kilojoules of heat are required to decompose 1.95

mol

NaHCO3 (s) ?

2NaHCO3 (s) + 1290 - Na2CO3 (s) + H20 (9) + CO2 (9)

126 13

258

129 la

• 2.53 x 107

253.02 kJ.

Explanation:

The balanced reaction for the decomposition of baking soda is

2 NaHCO3 (s) → Na2CO3 (s) + CO2 (g) + H2O (g)

We can find the heat of reaction by using the Hess' Law. This is done by using this formula:

∑ (Hf, products) - ∑ (Hf, reactants) = Heat of reaction

where Hf is the heat of formation. According to literature, these are the heats of formation for each of the compounds in the reaction:

NaHCO3: - 947.68 kJ/mol

Na2CO3: - 1130.94 kJ/mol

CO2: - 393.51 kJ/mol

H2O: - 241.8 kJ/mol

Applying Hess' Law:

[1 (-1130.94) + 1 (-241.82) ] + 1 (-393.51) ] - [2 (-947.68) ] = 129.09 kJ

Thus, the heat of reaction is 129.09 kJ/mol NaHCO3. Since there is 1.96 mol of NaHCO3, the total heat of reaction is 253.02 kJ.