Question

Use the balanced combustion reaction above to calculate the enthalpy of combustion for C8H16. C8H16(1)= -174.5kJ/mol. I have no clue how to start this question and need help including the formulas so I know how to do it and some step by step commentary.

Answer 1

Step-by-step explanation:

C₈H₁₆ + 12O₂ = 8 CO₂ + 8H₂O.

a )

Heat of formation of C₈H₁₆

`\triangle H_f (C_6H_(16))=-174.5 kJ`

`\triangle H_f (CO_2)=-393.5 kJ`

`\triangle H_f (O_2)= 0`

`\triangle H_f (H_2O)=-285.82 kJ`

`\triangle H_(reaction) =` 8 x - 393.5 - 8 x 285.82 + 174.5x 1

= - 5260.06 kJ

b ) Energy required = 2.905 x 10¹⁵kJ

moles of C₈H₁₆ require to be burnt

= 2.905 x 10¹⁵ / 5260.06

= 55.23 x 10¹⁰ moles

= 55.23 x 10¹⁰ x mol weight of C₈H₁₆ g

= 55.23 x 10¹⁰ x 112 g

= 6185.5 x 10¹⁰ g

= 6185.5 x 10⁷ kg

c )

No of litres of CO₂ produced at NTP = 8 x 22.4 x 55.23 x 10¹⁰ L

= 9897.22 x 10¹⁰ L

At 1520 mm of Hg pressure and 250°C

volume of CO₂

= 9897.22 x 10¹⁰ x 760 x ( 273 + 250) / ( 1520 x 273 )

= 9480.3 x 10¹⁰ L .