Question

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

Answer 1

253.02 kJ.

Step-by-step 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.