C=md/ms*100=>md=C*ms/100=49*400/100=196g H2SO4
MNa=23g/mol
MNa2SO4=2ANa+AS+4AO=2*23+32+4*16=142g/mol
2Na + H2SO4 = Na2SO4 + H2
a) 2*23g Na..............98g H2SO4
x=.........................196g H2SO4
x=46*196/98=92g Na
b) 98g H2SO4..................142g Na2SO4
196g H2SO4......................x=284 Na2SO4 (sare)
c) 98g H2SO4......................22,4L H2
196g H2SO4.........................44,8L H2