Question

The correct sequence of thermal stability of the following carbonates is
A: $BaC{O_3} < CaC{O_3} < SrC{O_3} < MgC{O_3}$
B: $MgC{O_3} < CaC{O_3} < SrC{O_3} < BaC{O_3}$
C: $BaC{O_3} < SrC{O_3} < CaC{O_3} < MgC{O_3}$
D: $MgC{O_3} < SrC{O_3} < CaC{O_3} < BaC{O_3}$

Answer 1

Hint: Thermal stability of compounds is measured by the temperature of decomposition. Temperature of decomposition means the temperature at which substance decomposes. Decomposition means breakdown or change of a material or substance.

Complete step by step answer:
Stability of carbonates of alkaline metals increases down the group because electropositive character of metal increases down the group. This means more heat will be required for decomposition. As we know thermal stability of compounds is measured by the temperature of decomposition. Among these given compounds metals according to increasing atomic number are magnesium, calcium, strontium, barium. So answer is option B that is $MgC{O_3} < CaC{O_3} < SrC{O_3} < BaC{O_3}$
Additional Information: Alkali metals are chemical elements from s block of the periodic table. These metals have silvery appearance and can be easily cut with the knife as they are very soft. These metals are highly reactive. They readily lose their outermost electrons to form cation. Going down the group reactivity of alkali metals increases, their atomic radius increases but their electronegativity, melting point and boiling point decreases. These metals react violently with water, halogens and acids. These reactions release high amounts of heat and light. Nitrates, carbonates and sulphates of alkali metals are water soluble their solubility increases down the group because their lattice energy decreases more rapidly than hydration energy, but in alkaline earth metals solubility of nitrates decreases down the group because their hydration energy decreases more rapidly than lattice energy. Hydration energy is the amount of energy released when a mole of ions undergo hydration. Lattice energy is that energy which is contained in the crystal lattice of a compound. It is equal to the energy that would be released if component ions were brought together from infinity.

Note: There exists a diagonal relationship between elements of group $1$ and group $2$. This means diagonal elements of these periods have similar properties. Properties of lithium resemble properties of magnesium, properties of beryllium resemble properties of aluminum and so on.