Which reactions are oxidation-reduction reactions? 1. fes(s) + 2hcl(aq) → h2s(g) + fecl2(g) 2. agno3(aq) + nacl(aq) → agcl(s) + nano3 3. 2c3h6(g) + 9o2(g) → 6co2(g) + 6h2o(g) 4. fe2o3(s) + 3co(g) → 2fe(l) + 3co2(g)

The correct answer is Option 3 and Option 4.

Explanation:

Redox reactions are termed as the reactions in which reduction and oxidation reactions occur simultaneously.

Reduction reactions are the ones where a substance gains electrons. The oxidation state of the substance gets reduced.

Oxidation reactions are the ones where a substance looses electrons. The oxidation state of the substance is increased.

Fro the given options:

Option 1:

This reaction is a type of double displacement reaction because exchange of ions takes place.

Option 2:

This reaction is a type of double displacement reaction because exchange of ions takes place.

Option 3:

On reactant side:

Oxidation state of Carbon = +2

Oxidation state of Oxygen = 0

On product side:

Oxidation state of Carbon = +4

Oxidation state of Oxygen = -2

Here, oxidation state of carbon is increasing from +2 to +4. Thus, it is getting oxidized and oxidation state of oxygen is getting reduced from 0 to -2. Thus, it is getting reduced.

Option 4:

On reactant side:

Oxidation state of Iron = +3

Oxidation state of Carbon = +2

On product side:

Oxidation state of Iron = 0

Oxidation state of Carbon = +4

Here, oxidation state of carbon is increasing from +2 to +4. Thus, it is getting oxidized and oxidation state of iron is getting reduced from +3 to 0. Thus, it is getting reduced.

Hence, the correct answer is Option 3 and Option 4.

- 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