Question

Which of the following reactions involves the combination of two elements :- a)CaO + CO2 -> CaCO3 b)4Na + O2 -> 2Na2O c)SO2 +(1/2)O2 -> SO3 d)NH3 + HCI -> NH4CI

Answer 1

Equation (b) involves the combination of two elements i.e sodium and two volumes of oxygen to form a new compound sodium oxide.

Answer 2

Answer:

The reaction $4Na + O_2 \rightarrow 2Na_2O$ involves the combination of 2 elements.

Explanation:

From the given reactions, we understand that all the 4 given reactions are combination reactions.

Combination reactions involve the combining of 2 reactants to form 1 product. This is of the form $A + B \rightarrow AB$

However, in the given reactions, only the reaction $4Na + O_2 \rightarrow 2Na_2O$ is of the combination of elements.

This, we can understand, because CaO, CO₂, SO₂, NH₃, and HCl are compounds, formed upon the reaction of 2 elements.

From this question, we can understand that there are subdivisions of combination reactions - involving different types of reactants - elements and compounds.

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