Question

When the enthalpy of this overall chemical equation is calculated, the enthalpy of the second intermediate equation

Answer 1

it is halved and the sign is changed by  the chemical reaction

Answer 2

Answer: The correct answer is Option 1.

Step-by-step explanation:

We are given two intermediate equations and a final net equation for the formation of calcium carbonate. To form a net equation, we have to apply some operations on the second equation.

Two intermediate equations given are:

`Ca(s)+CO_2(g)+(1)/(2)O_2(g)\rightarrow CaCO_3(s)`
`\Delta H_1=-812.8kJ`

`2Ca(s)+O_2(g)\rightarrow 2CaO(s)`
`\Delta H_2=-1269.8kJ`

To get the final equation, we will half the second equation and reverse the equation, we get:

Equation 1:
`Ca(s)+CO_2(g)+(1)/(2)O_2(g)\rightarrow CaCO_3(s)`

Equation 2:
`CaO(s)\rightarrow Ca(s)+(1)/(2)O_2(g)`

Net Equation:
`CaO(s)+CO_2(g)\rightarrow CaCO_3(s)`

Hence, the correct answer is Option 1.