Ans:- 84.3 g/mole 4) is correct option
The equation for the above reaction is as follows:-
M2CO3 + 2HCl-> 2MCl+CO2+2H2O
This shows that ,
1 mole of CO2 is produced from -> 1 mole of M2CO3
0.01186 mole of CO2 needs -> 1g of M2CO3
1 mole of CO2 needs -> (1g/0.01186mole)*1 mole = 84.31g
Hence, 84.31g being the mass of 1 mole of the carbonate is its molar mass.