When ethyl acetoacetate (ch3coch2co2ch2ch3) is treated with one equivalent of ch3mgbr, a gas is evolved from the reaction mixture, and after adding aqueous acid, ethyl acetoacetate is recovered in high yield. identify the gas formed and explain why the starting material was recovered in this reaction. be sure to answer all parts.

Methane gas is formed in this reaction. After adding aqueous acid, ethyl acetoacetate is reformed through protonation of it.

Explanation:    

acts as base towards ethyl acetoacetate. Because ethyl acetoacetate contains active methylene group.

Hence   abstracts a proton from methylene group and being converted to methane gas.

After addition of aqueous acid, conjugate base of ethyl acetoacetate gets protonated and ethyl acetoacetate is reproduced.

See the attachment below.

pie chart because it is in percents ( % )

the formula mass of a molecule or a compound is the sum of the atomic weights of the atoms in its empirical formula

(that's what i know about formula mass)