Question

Find the mass of ethane C2H6 required to produce 5000 kJ of heat.

C2H6(g) + 7 2O2(g) = 2CO2(g) + 3H2O(g),

∆H◦ = −1423 kJ/mol.

(C2H6) = 30.07 g/mol.

Answer 1

write the reaction as follows

C­_2­H­₆­(g) + 7/2 O­_2­(g)----------> 2CO_­2­ + 3H­_2­O(l);     ∆H^o = -1423 KJ/mol

from the above reaction we can observe that 1 moles of C­₂­H_­6­ burned in presence

of O_­2­ and releases 1423 KJ/mol of energy.

given amount of heat q = 5000 kJ

calculate the moles of   C­₂­H_­6­(n) as follows:

q = n∆H^o

n = q/∆H^o

n= 5000/ 1423

n = 3.514 mol

now calculate the mass of C­₂­H_{­6 ­} that is to be burned as follows :

molar mass of C­₂­H_­6­ = 30.07 g/mol

mass of C­₂­H_­6­ = moles of C­₂­H_­6 ­ X molar mass of C­₂­H_­6­

                        = 3.514 mol X 30.07 g/mol

                        = 105.66 g

therefore the required solution is 105.66 grams of C­₂­H_­6

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