Explanation

(b)
Calcium salts of carboxylic acid on heating give carbonyl compound.
$(a)(HCOO)_{2}Ca + \left( CH_{3}CH_{2}COO \right)_{2}Ca$
Calcium formate calcium propanoate
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ O$
||
$\rightarrow 2CH_{3}CH_{2}C - H + 2CaCO_{3}$
propanal
$(b)\left( CH_{3}COO \right)_{2}Ca + \left( CH_{3}CH_{2}COO \right)_{2}Ca$
Calcium acetate calcium propanoate
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ O$
||
$\rightarrow 2CH_{3} - C - CH_{2} - CH_{3} + 2CaCO_{3}$
2-butanone
$(c)\left( CH_{3}COO \right)_{2}Ca + \left( CH_{3}COO \right)_{2}Ca$
Calcium acetate calcium acetate
O
||
→$2CH_{3} - C - CH_{3} + 2CaCO_{3}$
acetone
$\ (d)(HCOO)_{2}Ca + \left( CH_{3}COO \right)_{2}Ca$
Calcium formate calcium acetate
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ O$
||
→$2CH_{3} - C - H + 2CaCO_{3}$
ethanal