Answer:
Step-by-step explanation:
CO2, CO, O2, Au, CH20, and Cl2 are the chemical compounds listed in the highlighted text.
CO2 is carbon dioxide, which has one carbon atom and two oxygen atoms. The oxidation state of carbon in CO2 is +4, and the oxidation state of each oxygen atom is -2. Therefore, CO2 does not have an oxidation state of zero.
CO is carbon monoxide, which has one carbon atom and one oxygen atom. The oxidation state of carbon in CO is +2, and the oxidation state of oxygen is -2. Therefore, CO does not have an oxidation state of zero.
O2 is oxygen gas, which consists of two oxygen atoms. The oxidation state of each oxygen atom in O2 is zero, but the compound as a whole does not have an oxidation state of zero.
Au is gold, which is a noble metal and does not usually form compounds with an oxidation state of zero.
CH20 is formaldehyde, which has one carbon atom, two hydrogen atoms, and one oxygen atom. The oxidation state of carbon in CH20 is 0, and the oxidation state of each hydrogen atom is +1, and the oxidation state of oxygen is -2. Therefore, CH20 has an oxidation state of zero.
Cl2 is chlorine gas, which consists of two chlorine atoms. The oxidation state of each chlorine atom in Cl2 is zero, and the compound as a whole has an oxidation state of zero.