Question

An element reacts with oxygen to produce a melting point compound. This compound is easily soluble in that element. a. Calcium b. Carbon c. Silicon d. Iron​

Answer 1

Answer:

a

Explanation:

The molecule is formed by the calcium cation Ca+2 and the oxygen anion O2-, which form an ionic bond.

Answer 2

Answer:

To solve such problems, we need to consider every option. So, let us react to each element given in the options with oxygen and write the chemical equation of each.

2Ca+O2→2CaO

C+O2→CO2

Si+O2→SiO2

2Fe+2O2→Fe2O4

But we can clearly see from these equations that each element is forming oxide on reacting with oxygen, so we can’t predict the further two things such as melting point and solubility with the help of these equations. Therefore, the next thing we need to look at is their melting points because then only we will be able to compare which one has the highest.

CaO:2614oC

CO2:−56oC

SiO2:1650oC

Fe2O4:1597oC

Now, we can clearly see that calcium oxide has the highest melting point out of the four oxides formed above. Also, the oxides of alkaline earth metals have highest melting points as compared to nonmetals or transition metals. Thus, we can say that the element is calcium.

We are also given that the compound formed is soluble in water i.e. calcium oxide is soluble in water and produces its hydroxide, so we can write the chemical reaction as:

CaO+H2O→Ca(OH)2

This can be clearly understood as ionic compounds have high melting and boiling points in general such as calcium oxide.Also, we know that highly reactive metals cannot be obtained from their oxides by heating them with carbon and iron vessels get a brown coat when left exposed to air in the rainy season due to rusting of iron.

Hence, the correct option is (A).

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