Which of the following correctly gives the sum of all the stoichiometric coefficients (reactants and products, smallest whole numbers) in the balanced equation for the action of concentrated $H X_{2} SO X_{4}$ and $MnO X_{2}$ on sodium bromide to give bromine, $NaHSO X_{4}$ , $MnSO X_{4}$ and water?

Answer: D

The balanced equation is

2 NaBr + MnO X_{2} + 3 H X_{2} SO X_{4} 2 NaHSO X_{4} + MnSO X_{4} + Br X_{2} + 2 H X_{2} O

(checked atom by atom). The coefficients are

2 + 1 + 3 = 6

on the left and

2 + 1 + 1 + 2 = 6

on the right, total 12.