Question

Care este concentratia de solutie de NaOH de concentratie procentuala masica 40% neutralizata de 100cm^2 solutie de HBr de concentratie molara 4 moli?

Answer 1

NaOH + HBr => NaBr + HOH
c NaOH = 40%
V HBr = 100 cm^3 = 100 ml (1 ml=1cm^3) = 0.1 L sol HBr
C HBr = 4 M

C= n/V => n= C x V = 0.4 mol HBr
m HBr = n x M => m HBr = 81 x 0.4 = 32.4 g HBr
M HBr = 81 g/mol
 
40 g/mol NaOH ... 81 g/mol HBr
    a g NaOH ........32.4 g HBr
a= 32.4 x 40/81 = 16 g NaOH 
md NaOH = 16 g
c NaOH = 40%
ms = md x 100 /c => ms = 16 x 100/40 = 40 g sol. NaOH 40%