[cuongt]

1.A 1.20g antacid tablet contains 80.0% by mass of magnesium hydroxide as the active ingredient. What volume of 0.1500molL^-1 hydrochloric acid could the antiacid tablet neutralise.

formula:   Mg(OH)2 +2HCl ----> MgCl2 + 2H2O

ratio of Mg(OH)2:HCl
                    1  :2
mass of Mg(OH)2= .8*1.2
                         =.96
n(Mg(OH)2)=m/M                                                                                      
                 =.96/58.3
                 =0.0165mol
  n(HCl)=0.0165mol*2
           =0.033mol                                   V=n/c
                                                               =.033/.15
                                                              =.22L
2.Oxidation number for sulfur is +6 in S2O4^2-?
3. Write ionin half equations for oxidation and reduction reactions that occur when sodium dithionite is mixed with water.

2S2O4^2-+H2O -> S2O3^2-+2HSO3^1-

one of the half equations i got was

S2O4^2- +H2O -----> S2O3^2-+2H^1+ +2e  wondering about the second one? or even if my first one is rite.

 

                                     

[xiankai]

1. seems correct to me

2. calculate for each sulfur atom individually

3. dont know too