Answer:MnCO3+2H2O----->MnO2+ HCO3-+2e-+3H+
Explanation:The equation to be balanced is
MnCO3 ------> MnO2+HCO3-
The oxidation number of Mn changes from +2 in MnCO3 to +4 in MnO2
Therefore two electrons must be added to the right as shown below:
MnCO3 -------> MnO2+ HCO3-+ 2e-Now,there is one negative charge HCO3- and 1 negative charge on the two electrons making a total of -3 charges on the right. There is zero charge on the left.
To balance the equation,add3H+on the right,to cancel out the charges.
MnCO3 --------> MnO2+HCO3-+2e-+3H+
Adding H2O to balance Hydrogen and Oxygen atoms:
MnCO3+2H2O ------->MnO2+HCO3-+2e-+3H+