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Stearic acid (C₁₈H₃₆O₂) is a fatty acid, a molecule with a long hydrocarbon chain and an organic acid group (COOH) at the end. It is used to make cosmetics, ointments, soaps, and candles and is found in animal tissue as part of many saturated fats. In fact, when you eat meat, you are ingesting some fats containing stearic acid.
(c) Calculate the heat (q) released in kJ and kcal when 1.00 g of stearic acid is burned completely.

Respuesta :

The heat (q) released in kJ and kcal when 1.00 g of stearic acid is burned completely is 3 × 10^6 kJ and 7.17 × 10^5kcal.

The balanced equation for the complete combustion of the stearic acid into gaseous products is given below.

C₁₈H₃₆O₂ (S) + 26O2 (g) ------ 18CO2 (g) + 18H2O (l)

∆H combustion

18 × ∆H of CO2 + 18 × ∆H of H2O – ( 1 × ∆H of C₁₈H₃₆O₂ 26 × (∆H of O2)

= 18 ( -394 KJ /mol ) + 18 ( -242 KJ / mol ) -1 ( 948 KJ / mol)+ 26 (O KJ /mol )

= -10500 KJ / mol.

What is mole?

Mole is defined as the ratio of given mass of substance to the molar mass of the substance.

Mole = given mass/molar mass

Given,

Mass of substance = 1 g

Molar mass of substance = 284

Moles = 1/284

Moles = 0.0035 mol.

Heat released = -10500/0.0035

= 3 × 10^6 kJ.

1kJ = 0.239kcal

3 × 10^6 kJ = 0.239 × 3 × 10^6 kcal

= 7.17 × 10^5kcal

Thus, we concluded that the heat (q) released in kJ and kcal when 1.00 g of stearic acid is burned completely is 3 × 10^6 kJ and 7.17 × 10^5kcal.

learn more about moles:

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