Consider the intermediate chemical reactions. 2 equations. First: upper C a (s) plus upper C upper O subscript 2 (g) plus one half upper O subscript 2 (g) right arrow upper C a upper C upper O subscript 3 (s). Delta H 1 equals negative 812.8 kilojoules. Second: 2 upper C a (s) plus upper O subscript 2 (g) right arrow 2 upper C a upper O (s). Delta H 2 equals negative 1, 269 kilojoules. The final overall chemical equation is Upper Ca upper O (s) plus upper C upper O subscript 2 (g) right arrow upper C a upper C upper O subscript 3 (s).. When the enthalpy of this overall chemical equation is calculated, the enthalpy of the second intermediate equation is halved and has its sign changed. is halved. has its sign changed. is unchanged.

When the enthalpy of this overall chemical equation is calculated, the enthalpy of the second intermediate equation is halved and has its sign changed.

Explanation:

Hess’s law of constant heat summation states that the amount of heat absorbed or evolved in a given chemical equation remains the same whether the process occurs in one step or several steps.

According to this law, the chemical equation is treated as ordinary algebraic expressions and can be added or subtracted to yield the required equation. This means that the enthalpy change of the overall reaction is equal to the sum of the enthalpy changes of the intermediate reactions.

The overall chemical reaction follows:

The intermediate balanced chemical reaction are:

(1)      

(2)    

The expression for enthalpy of the reaction follows:

Hence, when the enthalpy of this overall chemical equation is calculated, the enthalpy of the second intermediate equation is halved and has its sign changed.

A. is halved and has its sign changed.

Explanation:

just took the test on edge

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.