Equimolar amounts of Cl2(g) and CO(g) are injected into an evacuated, rigid container, where they react according to the equation below. Cl2(g)+CO(g)⇄COCl2(g) ΔHrxn=−109kJ/molrxn (a) If 7.0 g of CO(g) is consumed in the reaction with excess Cl2(g), how many moles of COCl2(g) are produced? (b) Which element is oxidized in this reaction? Justify your answer in terms of oxidation numbers.

0.25 moles of COCl₂ are been produced

The element that is oxidized is C, it changed the oxidation state from +2 in CO to +4 in phosgene.

Explanation:

Equilibrium reaction:

Cl₂(g)  +  CO(g)  ⇄  COCl₂(g)

Let's convert the mass of CO to moles:

7g . 1mol /28g = 0.25 moles

As ratio is 1:1, we can say that 0.25 moles of COCl₂ are been produced.

1 mol of chlorine reacts to 1 mol of carbon monoxide in order to produce 1 mol of phosgene.

Chlorine is been reduced:

Cl₂  +  2e⁻  ⇄  2Cl⁻

Change the oxidation state, from 0 (ground state) to -1. Oxidation state decreased.

Carbon is been oxidized.

In CO, carbon has +2 as oxidation state. In phosgene the oxidation state is +4. This oxidation state was increased, that's why it has oxidized.