CO(g) + 12 O2(g) → CO2(g)The combustion of carbon monoxide is represented by the equation above.(a) Determine the value of the standard enthalpy change, ∆HrxnD , for the combustion of CO(g) at 298 Kusing the following information. C(s) + 12 O2(g) → CO(g) ∆H298D = − 110.5 kJ mol−1 C(s) + O2(g) → CO2(g) ∆H298D = − 393.5 kJ mol−1

Answer : The standard enthalpy change for the combustion of CO(g) is, -283 kJ/mol

Explanation :

According to Hess’s law of constant heat summation, the heat absorbed or evolved in a given chemical equation is the same whether the process occurs in one step or several steps.

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

The combustion of will be,

The intermediate balanced chemical reaction will be,

(1)    

(2)    

Now we are reversing reaction 1 and then adding both the equations, we get :

(1)    

(2)    

The expression for enthalpy change for the reaction will be,

Therefore, the standard enthalpy change for the combustion of CO(g) is, -283 kJ/mol

- calcium has greater affinity to bond with electron receptors than hydrogen does and hence, it has the ability to replace hydrogen in most of its compounds.

- lithium has 2 valence electrons in the product because it can make only 1 bond with hydrogen. beryllium has 4 valence electrons in the product because it can only make 2 bonds. it has fewer electrons than neon and can react with electron donors. each hydrogen has 2 valence electrons, the same as helium.

- the covalent bond formed between carbon and hydrogen is polar because carbon is more electronegative than hydrogen and it attracts the bonded electron pair closer to itself, thus giving hydrogen a partial positive charge.

- a hydrogen bond is a relatively weak bond that hydrogen atoms make with the electronegative atoms nitrogen, oxygen or fluorine.

so the best choice is a.) 2 calcium (ca) atoms