For reduction of 1,4 dinitrobenzene when doing the equation I add h20 at end then count how many H's on right side which is 10 as 1,4diaminobenzene has 8, then on left there are 4H's on 1,4 dinitrobenzene. so that means you need 6(H). But how come in the actual equation there are sudddenly 4H20's