Carbonic acid (H2CO3) forms when carbon dioxide (CO2) dissolves in water according to this equation:

CO2+H2O->H2CO3

How many moles of CO2 must dissolve in an excess of water to produce 2 moles of H2CO3?

A. 3 mol

B. 2 mol

C. 1 mol

D. 4 mol

In order to determine how many moles of CO2 provide 2 moles of H2CO3, we must look at the balanced reaction and compare the coefficients of each compound.

CO2 + H2O - - > H2CO3

The equation above is already balanced; therefore, for every 1 mole of CO2, we get 1 mole of H2CO3.

2 moles H2CO3 x (1 mole CO2) / (1 mole H2CO3) = 2 moles CO2.

We simply convert the moles of H2CO3 to moles of CO2, which results in 2 moles of CO2 required to give 2 moles of H2CO3.