Experimental reaction coefficients calculated from data: Predicted coefficients

Question

Experimental reaction coefficients calculated from data: Predicted coefficients from balancing the chemical equation: KCIO, (s)KCI (s)+02(8) REFLECTIVE EXERCISES Are your experimentally determined coefficients the same as the coefficients determined by balancing the equation? If not, suggest possible errors? 1. Aluminum oxide decomposes to form aluminum metal and oxygen. Use the following data to calculate the coefficients for the reaction. 2. a. Write the balanced chemical equation for the decomposition of aluminum oxide. b. Calculate the coefficients for the reaction using the following data: Mass of Al20s: 6.02g Mass of Al: 3.21g Mass of O2: 2.86g Do the coefficients calculated using the experimental result match the coefficients in the balanced equation? c.

Explanation / Answer

The coefficients from balancing the chemical reaction:

2 KClO3 (s) = 2 KCl (s) + 3 O2 (g)

1. The experimentally determined coefficients are not same as that calculated from balancing the chemical equation. The possible errors are:

(a) The reaction does not reach to completion

(b) Some mass of the products are lost

(c) Instrumental errors

2. (a)

Decomposition of aluminium oxide: 2 Al2O3 (s) = 4 Al (s) + 3 O2 (g)

(b) Moles of Al2O3 = mass / molar mass = 6.02 g/ 101.96 g/mol = 0.06 mole

Moles of Al = mass / atomic mass = 3.21 g / 26.98 g / mole = 0.12 mole

Moles of O2 = mass / molar mass = 2.86 g / 31.998 g / mole = 0.09 mole

Mole ratio of Al : O2 : Al2O3 = 0.06:0.09 : 0.12 = 1: 1.5 : 2 = 2:3:4

So, the reaction is: 4 Al2O3 (s) = 2 Al (s) + 3 O2 (g)

(c) The experimentally determined coefficients are not same as that calculated from balancing the chemical equation.

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