Question

Din 500 g soluție naoh cu concentratia 20% si 80 g Ca, se obtine o solutir care:
A.contine 148 g ca (oh) 2
B.contine 328 g apa
C.contine 2, 5 moli de naoh
D.are concentratia procentuala in naoh de 8%
E.are concentratia procentuala in ca (oh) 2 de 19%
Ma puteti ajuta cu răspunsuri ? Mulțumesc anticipat :)

Answer 1

mdNaOH=500*20/100=100 g  n=m/M=100/40=2,5 moli    C. adevarat
mH2Odin sol. de NaOH = 500-100 = 400 g

Ca  + 2H2O-----> Ca(OH)2  + H2
40g   2*18g          74g     
80g      y               x= 80*74/40=148 gCa(OH)2     A. adevarat

y=80*2*18/40=72 g H2O se consuma  deci mai raman 400g-72g=328 g H2O           B.adevarat
msfinal= mdNaOH+mdCa(OH)2+m H2O=100g+ 148g+ 328g=576
 cNaOH=100*100/576=7,36 %   D. fals
cCa(OH)2=148*100/576=25,69%   E. fals