A 3.81-gram sample of NaHCO3 was completely decomposed in an experiment. 2NaHCO3 → Na2CO3 + H2CO3

In this experiment, carbon dioxide and water vapors combine to form H2CO3. After decomposition, the Na2CO3 had a mass of 2.86 grams.
Determine the mass of the H2CO3 produced.
Calculate the percentage yield of H2CO3 for the reaction. Show your work or describe the calculation process in detail.

We can't until we know what we are working with or on

Electron equations of the given changes are as follow,a)                              cu      →      cu⁺²  + 2e⁻b)                              mg⁺²  +  2 e⁻      →      mgc)                              cl⁻    →      cl  +  1e⁻d)                              s  +  2 e⁻    →      s²⁻e)                                o²⁻      →      o  +  2 e⁻f)                              p  +  3 e⁻    →      p³⁻g)                              fe²⁺    →      fe³⁺  + 1 e⁻h)                              s²⁻    →      s⁴⁺  +  6 e⁻