200mL dd A: [imath]HCl: 0,4 \ mol, \ H_2SO_4: \dfrac{m}{98} \ mol[/imath]
a) TN1: 25mL dd A => tỷ lệ là [imath]\dfrac{25}{200} = \dfrac{1}{8}[/imath]:
[imath]HCl: 0,04 . \dfrac{1}{8} = 0,05 \ mol, \ H_2SO_4: \dfrac{m}{98} . \dfrac{1}{8} = \dfrac{m}{784} \ mol [/imath]
[imath]n_{H_2 \ (TN1)}= \dfrac{1,12}{22,4}=0,05 \ (mol)[/imath]
[imath]\dfrac{m}{784}=0,025 \Leftrightarrow m = 19,6 \ (g)[/imath]
b) TN2: 30mL dd A: [imath]HCl: 0,4.\dfrac{3}{20}=0,06 \ mol, \ H_2SO_4: \dfrac{m}{98}. \dfrac{3}{20} = 0,03 \ mol[/imath]
[imath]m_{dd \ NaOH} = 16,36 \times 1,31=21,4316 \ (g)[/imath]
[imath]m_{NaCl} + m_{H_2SO_4}=0,06.58,5 + 0,03.142=7,77 \ (g) < 8,97 \ (g)[/imath]
[imath]\Rightarrow[/imath] chất rắn có NaOH dư
[imath]m_{NaOH \ dư}=8,97-7,77=1,2 \ (g)[/imath]
[imath]n_{NaOH \ p/u}=0,06+0,06=0,12 \ (mol)[/imath]
[imath]m_{NaOH}=0,12.40+1,2=6 \ (g)[/imath]
[imath]C \% _{dd \ NaOH}= \dfrac{6}{21,4316}.100 \approx 28 \ ( \%)[/imath]